Cambridge IGCSE Combined and Co-ordinated Sciences
Answers to end-of-chapter questions
Answers to end-of-chapter questions
All sample answers were written by the authors.
Biology
Chapter B1 Cells
1 a movement, growth, nutrition, sensitivity, excretion
b reproduction, respiration
2 a chloroplast
b mitochondrion
c cell membrane
d nucleus vacuole
e cell wall
3 aA chloroplast is an organelle that contains the
pigment chlorophyll. (A chloroplast is surrounded
by two membranes. Folded membranes inside
the chloroplast have molecules of chlorophyll
on them.) Photosynthesis takes place inside
chloroplasts, with the help of chlorophyll, which
absorbs energy from light.
b All cells have a cell membrane, which is a thin layer
of protein and lipid that surrounds the cell and
controls what enters and leaves it. Plant cells (and
bacterial cells) also have a thicker layer surrounding
them. In plant cells, this is made of cellulose. Cell
membranes are partially permeable. Cell walls are
fully permeable.
4 a
5 a A cell wall;
B chloroplast;
b they have cell walls;
[2]
they have chloroplasts;
c i
Measured diameter on image = 20.5 mm
[2]
[1]
(Note: the measurement depends on where the
outer limit of the cell is considered to be. It should
be the middle point of the two cell walls around
the adjacent cells. If the measurement has been
made from cell membrane to cell membrane,
it will be 19.1 mm. If it has been made from the
midpoints of the triangle of extracellular space at
each corner, it will be 21.1 mm.)
ii actual size = image size ÷ magnification
= 20.5 ÷ 250
= 0.082 mm or 82 µm
[2]
Chapter B2 Movement in and out of cells
1 aOsmosis. Water is at a high water potential (dilute
solution) in the soil and at a lower water potential
(concentrated solution) inside the root cells. It moves
through the partially permeable cell membrane,
down its water potential gradient.
bNeither. In this case, all the molecules in the saliva
move as one, like water flowing in a river. Both
diffusion and osmosis involve the random, individual
movement of molecules or ions.
cDiffusion. The ink particles move randomly, bumping
into each other and into the water particles,
gradually spreading throughout the water.
• be drawn with unbroken lines (no gaps in the line)
• have the correct proportions
• show each structure accurately and clearly
[5]
b Measured diameter on diagram = 36.5 mm
actual size = image size ÷ magnification
= 36.5 ÷ 0.6
= 60.8 mm (or 6.08 or 6.1 cm)
1
dDiffusion. The carbon dioxide particles move
randomly, and some will ‘bump into’ a stoma
in the underside of the plant leaf. There is a
low concentration of carbon dioxide inside the
leaf, because the plant uses it up very quickly in
photosynthesis. The carbon dioxide diffuses down its
concentration gradient, from the air into the leaf.
2 aThe sugar solution as a whole does not do anything.
We need to think about the individual particles in the
sugar solution – the water molecules and the sugar
molecules. Both of these move about randomly. The
water molecules can get through the tiny holes in
the tubing, but the sugar molecules are too big. What
will happen is that the water molecules will move
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
If Visking tubing containing a sugar solution is put
into a beaker of water, water will move from the
water into the sugar solution, by osmosis.
b It is true that plant cells do not burst in pure water,
but this is because the cell wall is strong enough
to prevent this happening. The cell wall is fully
permeable, and cannot stop water molecules going
through it. So the corrected sentence could be:
Plant cells do not burst in pure water because,
although water enters the cell by osmosis, the strong
wall prevents the cell from bursting.
c It is true that water will move out of a plant cell
by osmosis, if the cell is placed in a concentrated
sugar solution. However, the cell wall is not partially
permeable – it is fully permeable. So the corrected
sentence could be: When a plant cell is placed in a
concentrated sugar solution, water moves out of
the cell by osmosis, through the partially permeable
cell membrane.
d Plasmolysis is the result of placing a plant cell in
a concentrated sugar solution. So much water
moves out of the cell by osmosis that the contents
shrink, and the cell membrane pulls away from
the cell wall. As animal cells do not have a cell
wall, they cannot undergo plasmolysis. So the
corrected sentence could be either:
Animal cells shrink when placed in a concentrated
sugar solution. OR
Plant cells plasmolyse in a concentrated sugar solution.
3 aDiffusion is a result of the random movement of
molecules or ions. At higher temperatures, these
have more kinetic energy and move faster, so
diffusion happens faster.
b During daylight, plants photosynthesise. They
produce oxygen in their leaves, so the oxygen
concentration inside the leaf is higher than the
oxygen concentration in the air outside. Oxygen
therefore diffuses down its concentration gradient,
from the leaf and into the air.
c Visking tubing is a partially permeable membrane. It
has tiny, molecule-sized holes in it. Water molecules
are even smaller than the holes, so they can pass
through. Sugar molecules are much bigger than the
holes, so they cannot pass through.
d When it is placed in pure water, an animal cell
absorbs water by osmosis. This is because there is a
higher water potential outside the cell than inside it.
The extra water makes the cell swell, until it bursts.
e Plant cells are held in shape by their full vacuoles,
which push outwards against the strong cell wall,
producing a very firm structure. A plant cell like this
is said to be turgid. Turgid cells pressing against each
other make plant tissues strong and firm. When the
cells are not full of water, they are no longer turgid, and
their contents do not press outwards on the cell wall.
The cells, and the tissues in the leaves that they make
up, become soft and floppy. This is why the plant wilts.
4 athe movement of molecules / ions, down a
concentration gradient / from a high concentration
to a low concentration;
as a result of their random movement;
[2]
b i
70
Time for litmus to go blue / s
randomly back and forth through the holes. Because
there are more of them in the water than in the sugar
solution, their net movement will be into the tubing.
So the corrected sentence could be:
Answers to end-of-chapter questions
60
50
40
sample A
30
20
sample B
10
0
0
2
4
6
8
10
12
Distance along tube / cm
14
16
all points correctly plotted; lose one mark for any
incorrect point
neat best-fit line drawn;
[3]
ii ammonium hydroxide is alkaline;
[1]
iii A;
[1]
iv C’s concentration was between A and B;
specific evidence quoted to support this statement,
e.g. it took less time for it to travel 10 cm than A and
more time than B.[2]
5 a the pH is greater than 8;
[1]
b table is drawn with a ruler and has rows and columns
for dimensions of block and time taken to go colourless;
headings for both quantities include correct units –
including time / s;
times to go colourless are correctly recorded as 128
and 72 (with no units);
[3]
2
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
c i
diffusion;
[1]
iihydrochloric acid neutralised the alkaline
substance in the agar / the pH became less
than 8;
[1]
d block B had a greater surface area to volume ratio /
the distance for diffusion to the centre of the block
was smaller in block B;[1]
Chapter B3 Biological molecules
1 amonosaccharide, found in both plants and animals,
used as fuel in respiration
b polysaccharide, found in plants only, used as an
energy store in plant cells
c polysaccharide, found in plants only, used to make
cell walls
d polysaccharide, found in animals only, used as an
energy stores in (liver) cells
2 a
b
c
d
e
f
nitrogen (or sulfur)
amino acids
Benedict’s
lipid (fat) sucrose
sucrose
metabolism or metabolic reactions
3 Measure equal volumes of each solution into two
identical test tubes.
Add equal volumes of Benedict’s solution to each one.
Place both tubes into a water bath at about 80 °C. Do this
at exactly the same time. Watch carefully. The one that
changes to green or orange first, or the one that is the
darkest orange after a set length of time, is the one that
has the most concentrated solution of reducing sugar.
4
Substance Elements Carbohydrate, How to
One
it contains fat or protein? test for it function
haemoglobin C, H, O, N
3
protein
biuret test carries
oxygen in
the blood
glucose
C, H, O
carbohydrate
Benedict’s to provide
test
energy
starch
C, H, O
carbohydrate
iodine test stores
energy in
plant cells
enzyme
C, H, O, N
protein
biuret test speeds up
reactions
Answers to end-of-chapter questions
5 a a protein catalyst, which speeds up the rate at which
metabolic reactions take place
b a term used to describe the state of a protein
molecule that has lost its shape – often caused by
high temperature or extremes of pH; a denatured
enzyme molecule is unable to catalyse its reaction
because the substrate no longer fits into its
active site
c the substance that is changed into products by
an enzyme; the substrate fits into the enzyme’s
active site
d a new substance formed in an enzyme-catalysed
reaction
e the part of an enzyme molecule into which a
substrate molecule fits
6 a About 37 °C – human body temperature.
b About 2 – hydrochloric acid has a very low pH.
c At low temperatures, molecules have low kinetic
energy and move slowly. This means that the
frequency of collisions between enzyme molecules
and substrate molecules is also low.
d Above the enzyme’s optimum temperature, the
enzyme molecule begins to lose its shape – it is
denatured. This means that the substrate molecule
does not fit into the active site, so the enzyme cannot
catalyse the change of the substrate into products.
7 a
b
c
d
calcium;
water;
they both contain protein;
orange-brown;
it does not contain starch;
[1]
[1]
[1]
[2]
e protein, fat and carbohydrate;
[1]
8 a blue-black;
bthe blue-black colour would have disappeared
from parts of the plain paper.
c i
Time /
Number of new
Total number of
minutes areas where there
areas where there
had been a reaction had been a reaction
1
14
14
2
28
42
3
18
60
4
12
72
5
6
78
[1]
[1]
[2]
© Cambridge University Press 2017
ii
Number of new areas where
there had been a reaction
Cambridge IGCSE Combined and Co-ordinated Sciences
30
20
10
0
0
1
2
3
Time / minutes
4
5
time on x-axis and number of new areas on y-axis;
scales on both axes go up in even steps (e.g. 1, 2,
3 etc. on x-axis, 10, 20, 30 etc. on y-axis); both axes
fully labelled including units; all points accurately
plotted with small, neat crosses or circles with a
ring around them; straight lines drawn between
the points / good best-fit line drawn;
[5]
iii any two sensible suggestions about differences
between the goats, e.g. different ages, different
genders, different breeds, different concentrations
of enzyme in their saliva, how hungry they were
when the saliva was collected;
[2]
d continue for longer; take readings more often than
one minute intervals; include some discs that have
no enzyme in them / have boiled enzyme in them;
repeat the experiment two more times;
[max 3]
9 a sucrose molecules and enzyme molecules move
randomly; sucrose molecule collides with enzyme’s
active site; enzyme causes sucrose molecule to split
into glucose and fructose; reference to involvement
of water in this reaction; products / glucose and
fructose, leave the active site;
[max 3]
b i
optimum temperature for enzymes; temperature
kept constant because, pH is the independent
variable / temperature is a control variable;
[2]
ii no activity below pH 3; optimum / greatest
activity, is at pH 7; no activity above pH 11;
[3]
Chapter B4 Plant nutrition
1
4
Obtained from
Used for
Nitrates
the soil
making amino acids
and proteins
Water
the soil
photosynthesis,
maintaining turgor /
supporting tissues,
transporting substances
Magnesium
the soil
making chlorophyll
Carbon
dioxide
the air
photosynthesis
Answers to end-of-chapter questions
2 a A chloroplast is an organelle that contains the
pigment chlorophyll. Photosynthesis takes place
inside chloroplasts, with the help of chlorophyll,
which absorbs energy from light.
b The palisade mesophyll is closer to the upper surface
of the leaf than the spongy mesophyll. The cells in the
palisade mesophyll are tall and thin, while the cells in
the spongy mesophyll are more rounded. The palisade
cells contain more chloroplasts than the spongy cells.
More photosynthesis takes place in palisade cells
than in spongy cells. There are larger air spaces in the
spongy mesophyll than in the palisade mesophyll.
c Organic substances have been made by living
organisms, e.g. carbohydrates, proteins, vitamins.
Inorganic substances have not been made by
organisms, e.g. magnesium ions, water.
d Guard cells are pairs of sausage-shaped cells found in
the epidermis of leaves (usually in the lower epidermis).
The hole in between the pair of guard cells is a stoma.
3 a carbon dioxide + water → glucose + oxygen
b Carbon dioxide enters the leaf through stomata, by
diffusion from the air. Water enters the root hairs, by
osmosis from the soil and is then transported up the
xylem to the leaf.
c Glucose is used to make starch, or to provide energy
by respiration. Oxygen diffuses out of the leaf into the
air, through the stomata.
4 a Carbon dioxide diffuses through the stoma and then
through the air spaces, allowing it to reach the cells
in the palisade layer. Oxygen diffuses in the opposite
direction when photosynthesis is taking place. (When
you have learnt about transport in plants, you will also
find out that the air spaces are important for allowing
the movement of water vapour out of the leaf.)
b This means that light can pass straight through
these cells, so little light is lost before it reaches the
palisade cells, where it is used in photosynthesis.
c The larger the surface area, the more sunlight will
hit the leaf. This means that more energy can be
absorbed by chlorophyll, so more photosynthesis
can take place.
d The veins bring water from the soil to the leaf cells.
By branching, they can bring water close to every
cell. The cells need water for photosynthesis, and
to maintain their turgor, helping the leaf to be held
out straight.
5 a sucrose. This is a soluble sugar, which can dissolve in
water for transport. It is not too reactive.
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
b starch. This is an insoluble polysaccharide, which
can be stored as solid grains in cells and will not
interfere with the reactions that take place in the cell.
(It also does not affect the water potential of the cell;
if sucrose was stored, this would tend to draw excess
water into the cell by osmosis.)
6 a Leaf from plant A: all orange-brown;
Leaf from plant B: uncovered part blue-black;
covered part orange-brown;
b i
to break down the cell membranes so that iodine
solution and starch can come into contact;
[1]
ii to remove the chlorophyll;
c i
[3]
[1]
cover other areas with a simlar material that is
transparent (so that the only difference is whether
light can reach the leaf);
[1]
ii it controls a significant variable – having different
plants could affect the results / because one
plant might respond differently from another; [1]
d use a plant with variegated leaves;
destarch it;
then leave in the light long enough for it to make starch;
test a leaf for starch;
would expect green parts to go blue-black, white
parts to be orange-brown;
[max 3]
7 a i
F;
[1]
ii A;
[1]
iii D.
[1]
b i
little light is lost before it reaches the palisade
cells, where it is used in photosynthesis;
[1]
ii the waxy cuticle prevents water loss through this
surface of the leaf; [1]
iii bring water to the leaf; take sucrose away from
the leaf; help to support the leaf.
[max 2]
c i
carbon dioxide; water
[2]
ii some is used in respiration to release energy;
some is converted to starch for storage; some is
used to make cellulose cell walls for new cells;
some is converted to sucrose for transport to
other parts of the plant; some is converted, with
the addition of nitrogen, to amino acids; some is
converted to, fats / lipids [max 4]
Chapter B5 Animal nutrition
1 a i
calcium, vitamin D
ii carbohydrate, fat, protein
5
Answers to end-of-chapter questions
iii protein
iv fibre
v protein, iron
vi vitamin D
b There is a very wide range of possible answers.
Images B5.02 to B5.04, and Tables B5.02 and B5.03,
provide some examples. Answers can also be
checked against a table of nutrient values of foods.
Search on the internet for: 'food nutrient content
table' and select one that covers foods commonly
eaten in the relevant country.
2 a Digestion is the breaking down of large food
molecules into small ones. Absorption is the
movement of these small molecules through the wall
of the small intestine and into the blood.
b The small intestine is longer and narrower than the
large intestine. It is made up of the duodenum and
ileum, whereas the large intestine is made up of the
colon and rectum. Digestion and absorption of all
types of food molecules – including water – takes
place in the small intestine. Only water absorption
takes place in the large intestine.
c Enamel is the exceptionally hard outer layer of a tooth.
Dentine is a softer layer beneath the enamel. Dentine
contains living cells, but enamel does not.
d Bile is a greenish liquid made in the liver and stored
in the gall bladder, whereas pancreatic juice is made
in the pancreas. Both liquids flow along ducts into
the duodenum. Bile contains bile salts, which are not
enzymes but which help to emulsify fats (break large
droplets into small ones). Pancreatic juice contains
several different digestive enzymes that digest fats,
proteins and carbohydrates. Both bile and pancreatic
juice also contain sodium hydrogencarbonate, which
neutralises the acid from the stomach.
3 a A salivary gland
B oesophagus
C stomach
D pancreas
E duodenum
F ileum
G colon
H rectum
I anus
J liver
b i
A and D
ii C and D
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
Answers to end-of-chapter questions
iii D
diagram shows a molar tooth;
correct labels to:
enamel;
dentine;
pulp cavity;
nerves and blood vessels;
crown / root;
iv C
v F and G
vi I
4 ingestion
amylase
starch
mucus
oesophagus
hydrochloric
proteins
duodenum
small
pancreas
gall
fatty acids
glycerol
5 a vitamin C and vitamin D;
[1]
b they all already are small molecules; which can
pass through the walls of the ileum;
[2]
c any two dairy foods, bread;
[1]
d helps calcium to be absorbed; needed for making,
bones / teeth;
[2]
e anaemia; lack of energy;
iron is needed to make haemoglobin;
which transports oxygen around the body;
lack of oxygen means less respiration;
[max 3]
6 a A incisor;
B canine;
C molar;
[3]
b tooth A: cut off pieces of food; to help with ingestion;
tooth C: crush / grind, food; to increase surface area
for enzyme action; [4]
c
7 a i
blue-black;
[6]
[1]
ii starch is present;
[1]
iii rows 2, 3 and 4 show sugar absent, starch absent
and sugar absent;
b i
rows 5, 6, 7 and 8 show starch absent, sugar
present, starch absent, sugar present;
[2]
breaks down starch to sugar;
[1]
ii results show there is sugar in the water in the
beaker;
so sugar molecules have moved through the
membrane;
sugar molecules are small enough to pass
through the holes in the membrane;
[2]
small intestine / duodenum / ileum;
[1]
c i
ii blood / blood plasma / capillaries;
[1]
d its molecules are too big to be absorbed / to pass
through the wall of the small intestine;
[1]
8 a breakdown of large / insoluble molecules;
to small / soluble molecules;
[2]
b amylase;
[1]
c i
[1]
at the beginning;
ii maltose;
[1]
iii line is of similar shape;
line is above the 35 ºC line;
[2]
d to produce molecules that are small enough to be
absorbed / because starch molecules are too large
to be absorbed;
[1]
Chapter B6 Transport in plants
1 a
b
c
d
e
f
6
xylem vessel
xylem vessel
root hair
transpiration
stoma
potometer
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
b so plants can make more amino acids / proteins;
2 a and b root hairs
liquid
root cortex cells
liquid
xylemliquid
leaf mesophyll cells
liquid
air spaces in leaf
gas
stomata gas
to make more cells for growth;
1 a vena cava, right atrium, right ventricle, pulmonary
artery, lungs, pulmonary vein, left atrium, left
ventricle, aorta
b vena cava, right atrium, right ventricle, pulmonary artery
b, c and d
4 a 20;
[1]
b as wind speed increases, water uptake increases;
any use of manipulated figures (e.g. doubling of wind
speed from 2 to 4 metres per second results in 1.7
times the rate of water uptake); [2]
c light intensity; temperature; humidity;
[max 2]
more root hairs;
shorter root hairs;
decrease in length of root hairs is (much) greater
for plant B;[2]
iii less surface area;
so less uptake of mineral ions / water;
so less photosynthesis;
less glucose / starch / carbohydrate synthesised;
so less fuel for respiration / less energy available;
less nitrate reduces protein synthesis;
7
2 a Arteries take blood away from the heart; veins take
blood towards the heart. Arteries have thick, elastic
walls; veins have thinner walls. Arteries have a narrow
lumen; veins have a wider lumen. Arteries do not
have valves; veins have valves.
b Oxygenated blood contains a lot of oxygen
(combined with haemoglobin inside the red blood
cells) and is bright red. Deoxygenated blood contains
less oxygen, and is a duller purplish-red.
c An atrium is one of the upper chambers of the
heart, which receives blood and which has thin
walls. A ventricle is one of the lower chambers of
the heart, which has thick walls that pump blood
out of the heart.
d A red blood cell is a small cell with no nucleus,
indented, and containing a large amount of
haemoglobin. Its function is to transport oxygen.
There are several types of white blood cells, but most
are larger than red blood cells and they all have a
nucleus. They do not contain haemoglobin. Their
function is to fight pathogens.
3 a
b
c
d
e
4
[2]
ii both show same increase in number of root hairs
(per unit area);
[2]
Chapter B7 Transport in animals
3 a a section cut across something
5 a i
Answers to end-of-chapter questions
[max 3]
plasma
white cells
red cells
platelets and plasma
plasma
• Arteries: thick walls to withstand high-pressure
blood; elastic walls to withstand pulsing blood;
narrow lumen so blood moves through fast
• Veins: valves to keep low-pressure blood moving in
one direction; wide lumen to provide least resistance
to blood flow
• Capillaries: very narrow, so red blood cells have
to squeeze through and are brought close to cells
that require oxygen; very thin walls with gaps, so
substances can easily move between blood and
tissue fluid
• Xylem vessels: dead and hollow so nothing in the way
of water movement; narrow, so a tall column of water
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
can be supported without breaking; lignin in walls to
make them waterproof and to provide strength; pits
in walls to allow water to move sideways
• Phloem tubes: living but with no nucleus and only
a small amount of cytoplasm, so sap can flow
through; perforated end walls to allow sap to flow
through
5 a contains haemoglobin that combines with oxygen;
collects oxygen in lungs, releases it in body tissues; [2]
b protects against, disease / pathogens;
takes in and kills micro-organisms / bacteria /
pathogens;[2]
c to deliver requirements to body cells; e.g. oxygen /
glucose / other named nutrient; to remove waste
products from body cells; e.g. carbon dioxide /
other named waste product;
[max 2]
6 a Red cell in diagram measures 23 mm;
so magnification = 23 / 0.007;
= × 3285.
b it has no nucleus;
[3]
it has a depression in the centre / is a biconcave disc;
it contains haemoglobin.
c i
[3]
transporting oxygen;
ii it contains haemoglobin; which combines
reversibly with oxygen; it has a large surface area
to volume ratio; which speeds up the movement
of oxygen into and out of the cell; it is small; which
allows it to squeeze through very small capillaries;
it has no nucleus; which makes more room for
haemoglobin.
[max 3]
7 a 2;
[1]
b i
[1]
about 0.75 s;
ii explanation of measuring time between two
equivalent points;
[2]
c ventricle volume decreasing; because the muscle is
contracting;[2]
d when the ventricle contracts, the valve shuts; because
of the pressure of the blood pushing upwards on it;
when ventricle relaxes, valve opens;
[3]
e line follows the same pattern as the first, at the same
times, but does not rise to such a high volume; [2]
8 a A left atrium;
B bicuspid valve / atrioventricular valve;
C semilunar valve;
D right ventricle;
8
[4]
Answers to end-of-chapter questions
b E vena cava;
F aorta;
[2]
c coronary (arteries); plaques / cholesterol / fat
deposit, in artery wall; partly blocks artery; less
blood can flow through; less oxygen carried to
heart muscle; increased likelihood of blood
clotting;
[max 3]
d to keep the blood moving; to keep the blood
oxygenated; to remove carbon dioxide from the
blood;
[max 2]
e has a septum dividing the two sides of the heart;
oxygenated blood on the left and deoxygenated on
the right; both sides contract at the same time; more
muscle on the left side; so more pressure produced
on the left side; high pressure to most of body; low
pressure to lungs;
[max 4]
Chapter B8 Gas exchange and respiration
1 a protein synthesis, cell division, growth, movement,
passage of nerve impulses, maintaining a constant
body temperature
b respiration
c glucose + oxygen → carbon dioxide + water
2 a inspired air has more oxygen; inspired air has less
carbon dioxide; inspired air usually has less water
vapour
b Oxygen is used by body cells in respiration. Carbon
dioxide is produced by body cells in respiration.
Water evaporates from the lining of the lungs into the
air, so it is breathed out in expired air.
3 a the movement of oxygen into the body and the loss
of carbon dioxide
b the alveoli in the lungs
b any three of: large surface area; thin; good supply of
air containing oxygen; good blood supply
4 a
b
c
d
anaerobic
both
aerobic only in humans; both in yeast
both
5 The following sequence should be shown, in a diagram or
words: down trachea, bronchus, bronchiole, into alveolus
(by mass flow of air), across wall of alveolus into the blood,
by diffusion into a blood capillary into a red blood cell,
combines with haemoglobin, carried along the pulmonary
vein to the left atrium of the heart then to the left ventricle,
pumped out of the heart into the aorta, then to a capillary
in the arm muscle, diffuses out of the red blood cell,
diffuses out of the capillary, diffuses into the muscle cell
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
6 a i
to make sure all the carbon dioxide had been
removed;[1]
ii clear;
b i
[1]
to see if any carbon dioxide had been
produced;[1]
Answers to end-of-chapter questions
most of the graph paper provided; each bar drawn
neatly and precisely;
[4]
b the more cigarettes smoked per day, the greater the
chance of dying between the ages of 40 and 60 years old;
the younger a person is when they start smoking, the
greater the chance of dying between the ages of 40
and 60 years old;
ii cloudy;
[1]
c have another apparatus in which flask 4 has no
insects;[1]
d i
red / orange;
[1]
ii carbon dioxide present;
7 a
b
c
d
e
f
Chapter B9 Coordination and homeostasis
dissolves / reacts with water;
to produce an acidic solution;
e respiration ;
[3]
[1]
12;
[1]
21;
[1]
3
0.5 dm ;[1]
1.1 dm3;[1]
more rapid breathing brings fresh air into the lungs
more often; deeper breathing brings a larger volume
of fresh air into the lungs; more oxygen can diffuse
into the blood more quickly; supplying more oxygen
to the muscles; so they can respire faster; releasing
more energy from glucose;
[max 4]
brain senses the pH of blood; pH decreases during
exercise; because more carbon dioxide is dissolved
in the blood plasma; brain responds by sending more
frequent impulses to the breathing muscles; so they
contract harder and more frequently;
[max 4]
8 a 12.5 breaths per minute at start, 25 breaths per
minute during exercise; so increase is 12.5 breaths
per minute;
[2]
b from just before 11 minutes to just before 16 minutes;
5 minutes;
[2]
c during exercise not enough oxygen was supplied
to muscles; so they respired anaerobically (as well
as aerobically); producing lactic acid; which was
broken down by combining with oxygen (when
exercise finished); reference to paying back the
oxygen debt ;
[max 4]
d would follow a pattern similar to that of breathing rate;
heart pumps oxygenated blood to the muscles; more
oxygen required by muscles as they exercise; so that
they can respire faster; more carbon dioxide needs to be
removed from the muscles; continuing need for more
oxygen after exercise to pay off oxygen debt; [max 4]
9 a axes correctly labelled; x-axis scale uses the ranges
from the table; good scale on both axes that uses
9
the number of cigarettes smoked per day seems
to increase the chance of dying between 40 and 60
more than the age at which smoking started;
[3]
1 a a reflex action
b The stimulus from the sharp object is detected by
a receptor in the foot. This sends an electrical
impulse along a sensory neurone to the brain or
spinal cord. The impulse is passed along a relay
neurone and then to a motor neurone. This
transmits the impulse to an effector, the muscles in
your leg, and makes them contract.
2 a
b
c
d
e
motor and relay
sensory
sensory
motor, relay
relay
3 a
b
c
d
e
f
motor neurone
receptor
cornea
retina
contraction
circular
4 a Keeping the body temperature constant is just one
part of homeostasis, which is the maintenance of a
constant internal environment. Homeostasis also
involves the regulation of blood glucose concentration,
as well as the water content of the body.
b The hairs do stand on end when the body is too cold,
but in humans we do not have enough hair for this to
help to keep us warm. In other hairier mammals, the
raised hairs trap a layer of insulating air next to the skin.
c Air of any kind cannot get into the body through the
skin. The fat layer prevents heat leaving the body by
conduction, as it is an insulator.
d The sweat glands do secrete sweat onto the surface
of the skin when we are too hot, but this liquid is
not cold. It cools the body because the water in
the sweat evaporates, and this process takes heat
energy from the skin.
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
e The blood capillaries do not move at all. The
arterioles that supply the blood capillaries near the
surface of the skin get wider (dilate) when you are too
hot. This allows more blood to flow through these
capillaries, allowing heat to radiate from the blood
into the air.
f Insulin is a hormone, not an enzyme. Enzymes
catalyse reactions, but insulin is not a catalyst.
Insulin causes enzymes in liver cells to convert
glucose to glycogen.
5 a A 37.4 °C;
B 37.5 °C.
[2]
b homeostasis; humans are endothermic; body
produces more heat to maintain body temperature;
shivering; vasoconstriction;
[max 4]
c air is more insulating than water; heat lost more
easily from the body in water than in air; by
conduction;
[max 2]
d person A was moving but person B remained
still; idea that ‘new’ cold water was constantly
coming into contact with A’s skin; water around
B’s body warms up (as heat is lost from his body to
the water); heat transfers from hot object to cold
object; so more heat lost from A’s body than B’s
body;
[max 3]
6 a for respiration; by combining it with oxygen to
provide energy; (not ‘produce’ energy) for named
function (e.g. movement, active transport); [max 3]
b pancreas;
[1]
c i
starch digested to glucose; by enzymes / amylase
and maltase; absorbed into the blood from, the
small intestine / ileum;
[3]
ii insulin secreted; causes liver to take up glucose
from the blood; liver converts glucose to
glycogen; (also) glucose used by body cells in
respiration;
[max 3]
d negative feedback is a process that brings
concentration back to normal when it gets too high
or too low; when blood glucose concentration rises
too high, insulin is secreted and reduces it to normal;
when blood glucose concentration drops too low,
glucagon is secreted and raises it to normal;
[3]
7 a ability to detect changes in the environment;
and respond to them;
b i
gravitropism;
firm anchorage in the soil;
leaves have more light;
10
for photosynthesis;
[2]
iii builds up on the lower side;
causes cells in stem to elongate more;
causes cells in root to elongate less;
1 a
b
c
d
e
f
g
2
gamete
zygote
asexual
pollination
seed
fertilisation
sexual
Asexual reproduction
Sexual reproduction
only one parent involved
all offspring genetically
identical
one or two parents involved
involves gametes
involves fertilisation
zygote formed
genetic variation among
offspring
3 a i
age of seeds;
[1]
ii water; oxygen; warm temperature;
[3]
(if light also given, max 2 marks)
b i
young plants will get light for photosynthesis; [1]
ii D;[1]
4 a i
a sex cell;
joining together of nuclei of male and female
gametes;[2]
ii A – sepal;
B – produces pollen;
iii wall of ovary;
b B and C;
[2]
[1]
they have water;
they have a suitable temperature;
they do not need light;
[max 3]
tropism;
[2]
[1]
ii better photosynthesis;
[2]
[3]
Chapter B10 Reproduction in plants
c i
ii better access to water;
Answers to end-of-chapter questions
negative gravitropism;
because leaves can get more light;
flowers held up higher;
where insects can access them;
[2]
[max 3]
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
5 a asexual;
[1]
b produces new banana plants that are identical to
the parent (so the bananas will be exactly the same
variety); produces large new plants quickly;
[2]
c all new plants will be genetically identical; if the
parent did not have resistance to the disease then
nor will the offspring;
[2]
Answers to end-of-chapter questions
4 a
fetus to mother: carbon dioxide
and urea;
nucleus cytoplasm
cell membrane
[2]
flagellum
digestive enzymes
Chapter B11 Reproduction in humans
1 a
b
c
d
oviduct
ovary
uterus
cervix
all five labels correct three marks
2 a A uterus wall
B oviduct
C amnion
D amniotic fluid
E fetus
F placenta
G umbilical cord
H cervix
I vagina
b It produces amniotic fluid, in which the fetus floats.
This fluid protects it from bumps and knocks.
c The placenta brings the mother’s and fetus’s blood
close together, but does not allow them to mix. In
the placenta, useful substances such as oxygen and
glucose diffuse from the mother’s blood to the fetus’s
blood. Wastes such as urea and carbon dioxide
diffuse from the fetus’s blood to the mother’s blood.
3 a i
they are haploid / they have only one set of
chromosomes;[1]
ii it contains food stores for the developing embryo;
[1]
iii the food stores will soon run out; (once attached)
it obtains nutrients; and oxygen; from the
mother’s blood; through the placenta;
[max 4]
b i
A umbilical cord;
B amnion;
C cervix;
[3]
ii the (beating of the) fetus’s heart;
[1]
iii support / protect, the fetus;
[1]
iv mother to fetus: any two of oxygen / glucose
/ amino acids / water / other named soluble
nutrient;[2]
11
four labels correct two marks
two or three labels correct one mark
[3]
b acrosome contains enzymes which digest through
the jelly surrounding the egg; mitochondria release
energy by aerobic respiration (for swimming);
flagellum propels the sperm forwards; nucleus
contains the haploid number of chromosomes so
the normal diploid number is restored at fertilisation;
shape is streamlined to reduce energy needed
for swimming;
[max 4]
c nucleus contains the haploid number of
chromosomes so the normal diploid number is
restored at fertilisation; it contains food stores to
provide for the young fetus (until it is implanted); it is
surrounded by a protective layer of jelly;
[3]
5 a increased and then decreased; peaks in 2004 and
2007; any figure quote using both year and number of
people infected read from the graph;
[3]
b people recently infected with HIV show no symptoms;
may not have had their blood checked;
[2]
c more awareness of AIDS; people with HIV/AIDS now
knew that they had it and avoided passing it on;
people who were not HIV positive modified their
behaviour to reduce the risk of becoming infected
with HIV; example – avoided having multiple partners
/ used condoms / did not share contaminated
needles; use of antiretroviral drugs to treat AIDS;
other valid point.
[max 4]
Chapter B12 Inheritance
1 a a large letter for the smooth fur allele and a matching
small letter for the rough fur allele, using letters that
look different from each other, e.g. A and a (not S and s)
b AA, Aa and aa
c AA smooth fur, Aa smooth fur, aa rough fur
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
2 a a large letter for the red colour allele and a matching
small letter for the white colour allele, using letters
that look different from each other, e.g. R for the red
colour allele and r for the white colour allele
b R is dominant, because this is the allele that has
an effect in a heterozygous plant.
c RR, red; Rr, red; rr, white
3 a A gene is a length of DNA that codes for a particular
protein; an allele is one of two or more forms of a gene.
b A dominant allele shows its effect in a heterozygous
organism; a recessive allele only has an effect when
no dominant allele is present.
c A homozygous organism has two identical alleles
of a gene, e.g. AA; a heterozygous organism has two
different alleles of a gene, e.g. Aa.
d The genotype shows the alleles of a gene that an
organism possesses; the phenotype describes the
characteristics of the organism.
e Mitosis is a type of nuclear division in which
genetically identical daughter cells are produced;
meiosis is a type of nuclear division that produces
daughter cells with only half the full number of
chromosomes, and that are genetically different from
one another. Mitosis is used in growth, repair and
asexual reproduction; meiosis is used to produce
gametes.
f A haploid cell has one full set of chromosomes; a
diploid cell has two full sets.
4 a symbols should be the same letter, large and small,
and easily distinguishable, e.g.
EE for indented edges;
ee for smooth edges;
c
b parents’ phenotypes
indented
smooth
parents’ genotypes
EE
ee
gametes
E
e
all Ee
indented
parents’ genotypes correct;
gametes correct and placed inside circles;
offspring genotype and phenotype correct;
entire genetic diagram laid out correctly with
all headings;[4]
parents’ phenotypes
indented
indented
parents’ genotypes
Ee
Ee
E and e
E and e
gametes
spring genotypes and phenotypes
E
e
E
EE
indented
Ee
indented
e
Ee
indented
ee
smooth
parents’ genotypes correct; all gametes correct
and shown inside circles; genotypes of offspring
correct; phenotypes of offspring correctly associated
with genotypes; 99 : 302 is approx. 3 : 1 and genetic
diagram shows 3 indented : 1 smooth;
[5]
5 a i
white is dominant and himalayan is recessive – no
mark
upper case and lower case version of the same
letter chosen;
upper case for white and lower case for
himalayan;[2]
ii parents’s genotypes shown as Aa and Aa (or
whatever letters have been chosen in part a);
gametes from both parents shown as A and a
with circles around them;
offspring genotypes shown as AA, Aa, Aa and aa;
AA and Aa offspring identified as white, and aa as
himalayan;
ratio stated as 3 : 1 white to himalayan and
matched to three quarters white and one quarter
himalayan;[5]
[2]
spring genotypes
and phenotypes
12
Answers to end-of-chapter questions
b i
respiration;
oxidation of glucose / equation;
[2]
ii air trapped between hairs;
insulation;
reduces heat loss;
[max 2]
iii extremities / ears/ paws / nose, colder than other
parts of the body;
enzyme active only in these parts so black
pigment only produced there;
[2]
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
Chapter B13 Variation and natural selection
Answers to end-of-chapter questions
b i
1 species, discontinuous, genes, continuous, mutation,
adapted
2 a In continuous variation, an individual can
fit anywhere within a range of a particular
characteristic, with no sharp dividing lines. In
discontinuous variation, there are a small number of
distinct categories into which any individual fits.
b Natural selection is the increased chances of
individual organisms with particular variations
surviving and reproducing in their environment,
because of selection pressures that act on them.
Artificial selection is the choice, by humans, of
individuals with particular variations to be allowed to
breed together.
3 a Sexual reproduction allows mixing of alleles from
different parents. There is genetic variation in the
population. Different combinations of alleles may
give different features that make some individuals
better able to survive and reproduce in the
changing environment than their parents. Asexual
reproduction, however, produces offspring with
exactly the same combinations of alleles as their
parent; there is no genetic variation.
4 a correct answer given (you will need to get someone
to check!);
[1]
shape of ear lobes shows discontinuous variation;
so it is caused by genes
[2]
ii approximately 3 : 1; free : attached;
[2]
iii allele for free ear lobes likely to be dominant;
and allele for attached ear lobes likely to be
recessive;[2]
5 a i
There are no distinct categories; individuals
can have any wing length within the range from
63 mm or less to 70 mm or more;
[2]
ii for example: body mass / body length / beak
length;[1]
13
ii repeat measurements for a larger number of
birds; repeat in countries other than Sweden;
check wing lengths of birds that are breeding;
follow individual marked birds throughout their
lives to measure wing length and length of life;
measure the wing length of dead birds; [max 3]
c birds with this wing length survive for longer; more
likely to reproduce than birds with smaller wings;
wing length determined by genes / alleles which are
passed on to offspring;
[max 4]
Chapter B14 Organisms and their environment
(In both sexual and asexual reproduction, mutation
may occur, which could form new alleles that might
give an advantage to an organism and be selected
for. This is no more likely in sexual than in asexual
reproduction.)
b Mutation may produce new alleles that were not present
before. Although mutations usually produce new
characteristics that are less good than the normal ones,
just occasionally a new feature that gives an organism
a survival advantage may occur. If so, then this will be
selected for (its owners will be more likely to survive and
reproduce) and passed on to the next generation.
b i
the largest number of birds trapped has wing
lengths of 66 or 67 mm; suggesting that most birds
had these wing lengths; comparative data quoted
for birds with these wing lengths and others; birds
with these wing lengths had greater mean ages
when trapped; suggesting that they lived longer
than others; comparative age data quoted for
birds with these wing lengths and others; [max 4]
1 a A producer is an organism that makes its own
organic food materials from inorganic ones; plants
are producers, as they make organic nutrients by
photosynthesis. A consumer is an organism that
depends on organic nutrients made by producers;
animals and fungi are consumers.
b A primary consumer obtains its energy by feeding
on plants; it is a herbivore. A secondary consumer
obtains its energy by feeding on primary consumers;
it is a carnivore.
c A food chain shows how energy is transferred from
one organism to another, showing only one species
at each trophic level. A food web shows many
interlinking food chains, with more than one species
shown at each trophic level.
2 a to make carbohydrates, fats and proteins
b by photosynthesis; carbon dioxide from the air is
used to make carbohydrates
c They are given out from the plant as carbon dioxide.
d They break down carbohydrates, fats, proteins and
other carbon-containing materials in dead organisms
or waste products from them; they then respire,
giving out carbon dioxide to the atmosphere.
3 a i
sunlight;
ii chemical energy;
b i
respiration;
[1]
[1]
[1]
ii movement / muscle contraction; active transport;
generating heat to keep the body warm;
transmission of nerve impulses; building large
molecules from small ones;
[max 3]
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
c i
the food web should show an arrow going from
the wildebeest to ticks, another arrow going from
the ticks to the oxpeckers; and an arrow going
from the wildebeest to the oxpeckers;
[1]
ii energy is lost between trophic levels; 90% of
energy lost / only 10% of energy passed on; lost,
in respiration / as heat; so fewer organisms can
be supported at each trophic level;
[max 3]
4 a photosynthesis by aquatic plants; dissolving from
the air;
[2]
b bacteria feed on the sewage; so their populations
increase; bacteria respire; aerobically; use up oxygen
from the water;
[max 4]
14
Answers to end-of-chapter questions
c i
increasing quantities of untreated sewage running
into the river; build-up of nutrients in the water;
so larger bacteria populations used up more
oxygen;
[max 2]
ii sewage treated before entering the river; fewer
nutrients for bacteria; so fewer bacteria / less use
of oxygen by bacteria;
[max 2]
d they would die / leave the river;
[1]
e cause unpleasant smells; introduce pathogens
to the water that could cause disease in humans;
e.g. cholera bacterium; e.g. polio virus; other example
of water-borne disease-causing organism;
[max 2]
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
Chemistry
Answers to end-of-chapter questions
Chapter C2 The nature of matter
1 a Both ways of categorising substances have their use
to a chemist.
Chapter C1 Planet Earth
1 a i
• Knowing whether a substance is a solid, liquid
or gas at room temperature – and how easily
a substance can change its state – helps us in
handling the different substances and in separating
them and purifying them from mixtures. It is
important to realise that any substance can
exist in any of the three states, depending on the
conditions of temperature and pressure.
nitrogen 78%
Percentage in
unpolluted air
oxygen 21%
other gases 1%
[2]
ii carbon dioxide, argon, helium
b i
N2 + O2 → 2NO
[1]
[2]
ii that natural rain water is slightly acidic [1] /
from dissolved carbon dioxide [1] / after
thunderstorm more acidic because of
dissolved nitric acid [1]
[3]
2 a use cobalt chloride paper – turns from blue to pink;
or use anhydrous copper sulfate powder – turns from
white to blue
[2]
b as a coolant, or any other correct industrial use [1]
c a substance that dissolves another to form a
solution [1]
d i
burning coal in power stations or other correct
source [1]
ii kills fish in lakes, erodes statues/buildings
[2]
iii 64
e 1: filtration to remove solid particles
2: chlorination to kill bacteria/germs
f 21%
[1]
[2]
[2]
[1]
3 a lower proportions of oxygen and nitrogen; higher
proportion of carbon dioxide [1]
b acid rainfall causing damage to trees [1] /
acidification of lakes [1]
[2]
c add drops of the liquid to anhydrous copper(II)
sulfate powder (1); powder turns from white to
blue (1)
OR
add drops of the liquid to cobalt chloride paper (1);
colour change from blue to pink (1)
[2]
d methane
[1]
e burning of fossil fuels / volcanic activity
[1]
f neutralisation
[1]
g heating (thermal decomposition of) limestone in
furnace (kiln) [1]
CaCO3 → CaO + CO2[2]
15
• Knowing whether a sample is an element, compound
or mixture helps us in knowing and predicting
the chemical properties of a substance. These
distinctions are mutually exclusive and therefore are
more fundamental to our understanding.
b The word ‘particle’ is needed when talking in
generalisations about the structure and movement
of the constituents of matter. The context should
always be defined to distinguish this scientific use
of the word from the more everyday use when it
can be a speck of dust, etc. The one key experiment
where the two uses interact is in the description of
Brownian motion.
Here the unseen motion of atoms and molecules in
a fluid is demonstrated by the jerky, random motion
of the dust particles as they are hit by the submicroscopic particles that make up matter.
One aspect that can be discussed, and needs to
be referred to, is the key definition of the size of
the ‘particles’ involved when the term is used.
Descriptions such as ‘sub-microscopic’ and
‘subatomic’ are useful.
2 a i
The particles are in fixed positions [1]; they vibrate
about their fixed position [1].
[2]
ii Add water, stir to dissolve salt and filter to obtain
sand as the residue. [3]
b distillation, lower, volatile, condenser, vapour [5]
3 a seawater
b evaporation [1]; freezing (solidification) [1]
[1]
[2]
4 a A: thermometer; B: beaker
b to keep the temperature the same throughout [2]
[1]
c i
48 °C [1]
ii 72 °C d The particles are close together but irregular [1];
the molecules are able to move about with slow
movement [1]. [1]
[2]
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
e
i The third statement is correct: its melting point is
different from pure stearic acid. [1]
ii in testing medicines or food additives, or other
correct[1]
5 a balloons b i
nucleus
[1]
[1]
ii The third statement is correct: helium has a
complete outer shell of electrons.
[1]
iii 34 [1]
34
iv 18 Ar [1]
c The atoms are arranged irregularly [1] and are close
together/touching [1]. [2]
6 a electrons
b P has 2 protons and 2 neutrons (= 4 nucleons)
Answers to end-of-chapter questions
4 a i
ii E
iii F
iv B
v A[5]
b i
Correct electron structure of the F ions (electrons
from outer orbit of C moved to the two F atoms,
one electron to each to give eight electrons in
the outer shell of each)
[1]
Correct charges on each ion: – on F and
2+ on C[2]
−
[1]
F
[1]
c atoms are electrically neutral because they have
equal numbers [1] of protons
and electrons [1]
D
[C]2+
−
F
[2]
d R[1]
e 2.2
[1]
ii high melting point, soluble in water, conducts
when dissolved or molten, brittle (any two of
these possible answers) [2]
[3]
5 a i
Chapter C3 Elements and compounds
1 a helium / aluminium / chlorine
b i
B and C[1]
ii C[1]
iii D[1]
2 a Period 2
b i
[1]
O
ii F
iii Li
v Be
vi N c atoms, protons [6]
[2]
3 a hydrogen
[1]
P is in Group I / Q is in Group VIII (or 0) / R is in
Group VII [1]
the Group number is given by the number of
outer electrons in the atom [1]
ii Q is the least reactive as it is a noble gas
[2]
[1]
iii P is a good conductor of electricity as it is a
metal[1]
16
ii Y reacts with X, Z does not
b i
the elements are too reactive
[1]
[1]
ii An electron is transferred (donated) from a
sodium atom to a chlorine atom [1]; the sodium
becomes a positive ion and the chlorine a
negative (chloride) ion [1]
[2]
Chapter C4 Chemical reactions
iv C
b i
X conducts electricity, Z does not; or X reacts
with water, Z does not
[1]
1 a There is a colour change which shows that there
might be a reaction, and new substance(s) are
formed / a gas is given off.
b The most reliable evidence for a chemical reaction
is that a gas is given off which can be identified as
carbon dioxide.
c copper carbonate → copper oxide + carbon dioxide
zinc carbonate → zinc oxide + carbon dioxide
d Zinc oxide is a white solid which turns yellow when
heated. When cooled, the solid turns white again.
e No, it is a physical change.
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
2 a black solid b magnesium + carbon dioxide
→ magnesium oxide + carbon c i
carbon dioxide
ii magnesium
d MgO + 2HCl → MgCl2 + H2O [correct formulae but
unbalanced = 1] e i
Zn2+ + Mg → Mg2+ + Zn [1]
iii lime/calcium oxide, or slaked lime/ calcium
hydroxide d Fe + 2HCl → FeCl2 + H2 [1]
3 Step 2: Filter to remove excess solid [1]
[1]
Step 3: Evaporate to crystallisation point [1]
[2]
Step 4: L eave solution to cool [1]; dry crystals on filter
paper [1]
[2]
[2]
3 a sulfur + oxygen → sulfur dioxide [1 for reactants;
1 for product] b SO2 is oxidised to SO3 and O3 is reduced to O2 c SO3 + H2O → H2SO4 [2]
[2]
[1]
4 a aqueous sodium chloride, copper, graphite
[deduct 1 for each incorrect answer] b insulator [3]
[1]
anode [1]
ii negative = zinc [1] ; positive = chlorine [1] [2]
iii carbon [1]
5 a carbon/platinum [1] because unreactive [1] b bubbles [1] at both electrodes [1] c hydrogen at cathode [1], chlorine at anode [1] [2]
[2]
[2]
Chapter C5 Acids, bases and salts
1 a pH 11 b slaked lime c i
[1]
[1]
to help plants grow better (or words to that
effect)[1]
ii sulfur dioxide [1] from power stations [1] or
nitrogen oxides [1] from car exhausts [1]; dissolves
in rain [1] [3]
d i
neutralisation [1]
ii Measure the calcium hydroxide/alkali with a
pipette [1], add indicator [1] and add acid from
burette until there is a colour change [1]. [3]
2 a pH 3 [1]
b Add blue (or neutral) [1] litmus [1]; if it turns red, it is
acidic [1].
[3]
c i
calcium carbonate + hydrochloric acid → calcium
chloride + carbon dioxide + water [1 mark for each
product] [3]
ii in a blast furnace for producing iron
17
[1]
[2]
[1]
ii Magnesium reduces zinc ions [1] by donating/
giving electrons to them [1] [2]
c i
Answers to end-of-chapter questions
4 a i
ammonia gas is produced by the reaction [1];
ammonia turns moist red litmus blue [1]
[2]
ii no reaction if solid is ammonium nitrate [1]
white precipitate if solid is ammonium
sulfate [1]
[2]
b calcium carbonate reacts with acids [1]; calcium
carbonate will neutralise acidic soil [1]
[2]
5 a acidic: < 7, any appropriate e.g. SO2 basic: > 7, any
appropriate e.g. CaO neutral: 7, any appropriate
e.g. H2O [6]
b i
an oxide/substance that will react with/ dissolve
in both acids and alkalis
[1]
ii any strong acid (e.g. HCl) + any strong alkali
(e.g. NaOH)
[2]
Chapter C6 Quantitative chemistry
1 a
b
c
d
ammonia + sulfuric acid → ammonium sulfate 8
98
6.6 g
[1]
[1]
[1]
[2]
2 a 1.0 kg = 1000 g of conc. H2SO4 solution
mass of H2SO4 = (1000 × 98) / 100 = 980 g (molar
mass H2SO4 = 98 g/mol)
number of moles H2SO4 = 980 / 98 = 10 moles [3]
b i
molar mass of CaO = 56 g/mol [1]
number of moles CaO = 168 / 56 = 3 moles [1]
[2]
ii molar mass of H2O = 18 g/mol
reacting ratio is 1 : 1
3 moles of water = 3 × 18 = 54 g
[2]
3 40/1000 × 2 = 0.08 moles; 0.08/2 = 0.04 moles; 0.04 moles;
0.04 × 238 = 9.52 g [4]
0.08 moles; 6/119 = 0.05 moles [1]
This is more than was necessary to react with all the
HCl as 0.05 > 0.08/2 [1]
[1]
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
Chapter C7 How far? How fast?
e i
1 The methods used to prevent explosions from ‘runaway
reactions’ are precisely the opposite to those changes
that would speed up the rate of reaction. The changes
used would need to have a ‘dampening’, or inhibitory,
effect. The following changes would all result in a
slowing down of a reaction:
• lowering the temperature
• adding water to dilute the reactants (see Workbook
Exercise 7.6 for an example)
• lowering the pressure of a gas reaction.
2 a hydrated iron sulfate
→ anhydrous iron sulfate + water [1]
b endothermic [1]; heat has to be applied (or words
to that effect) [1]
[2]
c pale green [1]
d It is a reversible reaction [1], hydrated iron sulfate
is formed [1] and heat is also generated (reaction
exothermic) which produces steam [1]. [3]
e reversible reaction [1]
f If water is added to anhydrous cobalt chloride [1], it
changes colour from blue to pink [1].
[2]
3 a Carbon dioxide is given off. somewhere between 600 and 630 s
respiration [1]
ii a substance which speeds up a chemical
reaction [1]
4 a amount of manganese(iv) oxide and temperature [2]
b i
the higher the concentration, the faster the
reaction [1]
ii A lower concentration will produce less oxygen. [1]
iii 25 or 26 s [1] 36 or 37 cm3[1]
c magnesium oxide, copper(ii) oxide, manganese(iv)
oxide, lead(iv) oxide [1]
5 a i
Other methods are also possible.
b i
Answers to end-of-chapter questions
fair test [1]; keep the amount of solution above
the cross the same [1] [2]
ii value for gap: between 120 and 150 [1]
iii speed decreases [1] because lower concentration
[1] means fewer collisions [1] [3]
b The reaction is faster [1] because higher temperature
makes particles move more rapidly [1]; this means
more collisions [1] and harder/more energetic
collisions [1].
[4]
6 a temperature, surface area of magnesium;
[1]
(length, mass or size of magnesium (ribbon) would
be allowed, simply writing ‘amount of magnesium’
not allowed)
[1]
b i
[1]
B
the graph shows a higher rate / is steeper;[1]
ii X placed at the beginning of the curve (see graph
below) [1]
ii (maximum volume of gas) 40 cm3 at reaction time
of 5 minutes / 300 s (1);
iii sketch graph to the right of the printed curve [1]
and levelling out above it [1]
[2]
average rate = 40 ÷ 5 = 8 / 40 ÷ 300 = 0.13 (1);
units: cm3 / minute or cm3 / s (1)
c i
Mass of flask and contents / grams
100.4
in aqueous (solution) / dissolved in water / in
solution;[1]
100.3
ii same mass / length / size / amount of magnesium
used in both experiments (1);
100.2
acid in excess / all magnesium used up in both (1);
gas volume produced depends on amount of
magnesium used (1)
[2]
100.1
100.0
0
c i
Chapter C8 Patterns and properties of metals
100
200
300
400
500
Time / seconds
600
700
gets faster [1]
ii gets faster d combustion, small, large [1]
[3]
18
[3]
1 a Alloys are metals whose composition is designed
to suit the properties required by a particular use
or situation. Properties which have been significant
in the development of alloys have included:
• tensile strength
• hardness
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
•
•
•
•
resistance to corrosion
Chapter C9 Industrial inorganic chemistry
electrical conductivity
1 Although there are some cases where recycling has
significant economic advantages in terms of costs (for
example, the recycling of aluminium), this is not always
the case. The most important argument for recycling is
the conservation of natural resources, particularly nonrenewable resources of minerals and fuels, for instance.
low melting point
colour.
b Brass is used in plugs and switches because, even
though it is not as good a conductor as copper, it is
cheaper and harder. It is more resistant to hard wear
and regular use.
2 a i
copper, zinc, magnesium, calcium [1]
ii Iron does not react with cold water [1] but it does
react with steam when heated [1].
[2]
b zinc + water → zinc oxide + hydrogen [1]
c high melting point/boiling point, malleable, conduct
heat, conduct electricity (any three)
[3]
d i
any sensible answer above 98 °C ii decreases [1]
[1]
iii any sensible answer above 0.53 g/cm3 and below
1.0 g/cm3 (it floats on water) [1]
3 a i
lithium + water → lithium hydroxide + hydrogen
[2]
[1]
ii 2Na + 2H2O → 2NaOH + H2 b lithium reaction not exothermic enough to melt
the metal, sodium and potassium melt into a ball,
potassium ignites spontaneously order of increasing
reactivity Li<Na<K all float on water, all fizz and
produce hydrogen, all leave an alkaline solution
(any five points) [5]
c i
anode: E [1]; electrolyte: A [1] [2]
ii positive = chlorine; negative = sodium
[2]
iii graphite d low melting point, soft/can be cut with knife,
electrical conductivity, etc. (any two) [1]
[2]
4 a i
Mg + 2HCl → (MgCl2) + H2
formulae (1); balancing (1)
[2]
ii magnesium > X > copper
[1]
b i
solution turns blue to colourless / becomes
fainter (1);
brown deposit (of copper) (on metal X) (1)
[2]
ii X is less reactive than magnesium / magnesium
is more reactive than X
[1]
c i
removal of oxygen / gain of electrons
[1]
ii metal ions have a positive charge (1); cathode
has a negative charge and opposite charges
attract (1)
[2]
19
Answers to end-of-chapter questions
The impact of efficient recycling can be wide-ranging.
The demand for rare metals for the electronics and
media industries puts great pressure on the need to
find new mineral resources and the development of
new mining ventures. This can bring conflicts with
environmental concerns in some of the most untouched
areas of the world. Efficient recycling could delay some
of these potential clashes of interest.
2 a acidic soil
[1]
b nitrogen
[1]
c ammonium sulfate + calcium hydroxide → ammonia
+ water + calcium sulfate products or ‘double
decomposition’[2]
d CaCO3[1]
e CaCO3 → CaO + CO2[2]
f water is added
[1]
g N2 + 3H2 ⇌ 2NH3; high pressure, moderate
temperature (or values), catalyst [4]
h 2SO2 + O2 ⇌ 2SO3; moderate temperature,
catalyst [4]
3 a A: yes will rust, has air and water [1];
B: no, has air but no water [1];
C: no, has air and water but protected/coated with
zinc [1] [3]
b carbon burned off by oxygen as carbon dioxide [1];
phosphorus, etc., react with calcium oxide/lime to
form slag [2] [3]
c surgical instruments, chemical plant, cutlery (any
of these) [1]
4 redox reaction: Fe2O3 + 3CO → 2Fe + 3CO2 (or give the
equation with carbon)
acid/base reaction: CaO + SiO2 → CaSiO3
Carbon burns to give heat and form carbon dioxide.
Carbon dioxide reacts with carbon to form carbon
monoxide.
Carbon monoxide reduces hematite to iron.
Limestone decomposes to calcium oxide and carbon
dioxide.
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
• the synthetic and natural polymers that provide us
Calcium oxide (lime) reacts with silica to form slag.
(two equations plus three other points of description) [5]
5 a i
oxygen = top left [1]
ii slag = right [1]
iii molten steel = bottom left
[1]
b i
They are gases.
[1]
ii They react together to form calcium phosphate,
which is a solid, and form slag, which floats on
the steel. [3]
c i
D
ii surgical instruments, chemical plant, cutlery
(any of these) [1]
[1]
6 a decomposition [1]
b so that the ions are free to move [1]
c to lower the operating temperature by lowering the
melting point of the electrolyte [1]
d B
[1]
e anode = oxygen or carbon dioxide [1]; cathode =
aluminium [1] [2]
f because they burn away [1] in the oxygen [1] [2]
3+
–
g Al + 3e → Al [1]
h pans, cans, power cables, aircraft bodies, etc. [1]
7 a i
reduction
Answers to end-of-chapter questions
[1]
ii carbon monoxide
[1]
iii coke (carbon) and hot air
[1]
b copper is less reactive than iron / bonding in copper
oxide is weaker (1); less energy needed to break
bonds (1)
[2]
c limestone is added to the blast furnace (1); limestone
decomposes in the furnace to give calcium oxide /
lime (1); silicon dioxide reacts with calcium oxide to
produce slag / calcium silicate (1)
[3]
with food, clothing and structural materials that
support our living and the technologies we
depend on
• the novel structures that provide the scope for
developing nanotechnology.
2 a i
hydrogen and carbon contain just one type
of atom; compounds contain different atoms
bonded together
elements are listed on the Periodic Table;
compounds are not
[2]
ii draw a central C with four hydrogens attached
by single bonds
[2]
iii natural gas
b i
[1]
Z[1]
ii X, Z
unsaturated molecules contain double bonds [2]
iii pass the gas through bromine water [1]; an
unsaturated hydrocarbon will decolorise the
bromine water [1], a saturated hydrocarbon will
not [1]
[3]
3 a a family of organic compounds with similar chemical
properties due to the presence of the same
functional group [1]
b A = alkene; B = alkane; C = alcohol [3]
c test: bromine water; A: decolorises; B: no effect [3]
d heat it with steam [1] and a catalyst [1] [2]
e fermentation [1]
4 a ethane (1); C2H6 (1)
b i
[2]
a homologous series
[1]
ii methane (1); CH4 (1)
[2]
iii
Chapter C10 Organic chemistry
1 The versatility of carbon lies in its ability to form chain
and ring structures, and to form multiple bonds with
itself and other atoms. The complexity that arises is
important to us in several different ways:
• the chemistry of life and the interactions between
carbon-containing molecules that generate the
energy for living cells and the way of passing genetic
information from one generation to the next
• the carbon-containing compounds – from fossil
[2]
c the boiling point of the alkanes increases with
the size of the molecule (1); the larger (longer) the
molecule the greater the forces (interactions /
inter-molecular forces) between the molecules (1);
more energy is needed to disrupt/break/overcome
these forces (1)
[3]
fuels – that are the fuels of our modern transport and
energy-generating systems
20
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
d i
3 a i
CH4 + 2O2 → CO2 + 2H2O
formulae (1); balancing (1)
[2]
ii number of moles carbon dioxide =
480 / 24000 (1) = 0.02 mol (1)
[2]
iii from equation: number of moles of methane used
= 0.02 mol (1)
Mr of methane = 16 (1)
mass of methane burnt = 0.02 x 16 = 0.32 g (1) [3]
1 The products of burning methane, ethanol and fuels
such as gasoline are the same – the question is more
one of the efficiency and our ability to use the fuels
cleanly. Methane and ethanol are single compounds
but gasoline is a mixture of hydrocarbons and more
difficult to burn completely. Incomplete combustion
gives rise to pollution with carbon monoxide, soot and
particulates.
Ethanol is more environmentally friendly because it is/
can be a renewable fuel. Any carbon dioxide released can
be at least partially removed from the atmosphere as (for
example) the sugar cane used in fermentation is grown.
Methane is more environmentally friendly as it produces
less carbon dioxide for the amount of energy it releases
as it has the best/highest carbon : hydrogen ratio.
2 a i
hydrogen and carbon
(each) contains one type of atom / is found in
the Periodic Table / cannot be broken down into
simpler substances;
propane
contains different atoms (or elements) bonded
together / can be broken down into simpler
substances / into elements
[2]
ii petroleum / natural gas
[1]
iii fractional distillation
[1]
iv heating / lighting / burners / cooking / vehicle
fuel / refrigerant / feedstock
[1]
(catalytic) cracking
[1]
ii only single bonds (in a molecule) / contains
maximum possible hydrogen atoms
[1]
iii ethene and propene
[1]
iv structure of ethene: draw two C linked by a
double bond, four H attached by single bonds
(two to each C)
[2]
21
structure of ethene: draw two C linked by a
double bond, four H attached by single bonds
(two to each C)
[2]
ii molecule contains at least one C=C double bond;
does not contain the maximum possible number
hydrogen atoms
[1]
b i
many ethene molecules join together to make a
long chain; draw a series of units joined together
[2]
Chapter C11 Petrochemicals and polymers
b i
Answers to end-of-chapter questions
ii addition polymerisation
[2]
4 a boiling point [1]
b fuel oil – fuel for home heating; kerosene – jet fuel;
lubricating fraction – waxes and polishes; naphtha –
making chemicals [4]
c i
heat and catalyst [2]
ii C14H30 → C2H4 + C12H26 iii H
[1]
H
C
C
[1]
H
H
d poly(ethene) [1]
e i
[1]
steam
ii a substance that speeds up a reaction 5 a i
a group of hydrocarbons with boiling points
close together [1]
[1]
ii C12H26 → C2H4 + C10H22 [1]
b heating and cooking; fuel for cars [2]
c molecules contain a double bond; a compound of
carbon and hydrogen only [2]
d i
catalytic addition of steam
ii
H
H
H
C
C
H
H
[1]
O
H
[2]
e monomers, polymers [2]
6 a condensation polymer
[1]
b i
20
[1]
ii Mr = (1 x 16) + (14 x 2) + (12 x 6) = 116
[2]
c
(at least) three monomer units shown (1); correct
sequence (1); amide links shown (1)
[3]
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
d it (is a covalent substance) does not conduct
electricity[1]
f
i
f
correct plotting [2]; two straight lines [1] [1]
it is a gas which absorbs heat (1); retains heat in
the atmosphere / raises the temperature of the
air (1)
[2]
ii by catalysing a reaction between nitrogen dioxide
and carbon monoxide (1); to produce carbon
dioxide and nitrogen (1)
[2]
[3]
1.20
1.00
Total increase in mass / g
e the molecules are not all the same length / it is a
mixture of molecules (of different lengths)
Answers to end-of-chapter questions
0.80
0.60
0.40
0.20
Chapter C12 Chemical analysis
and investigation
0.00
2 a arrow under copper oxide b black [1] to orange/brown/pink [1] c diagram of condenser tube through [1] cooling
jacket [1] d extinguished [1]
[2]
3 a carbon or platinum b cathode (negative electrode) c bubbles [1]
[1]
[1]
d i
with an organic solvent – ethanol or
propanone ii using a hair dryer
e 0.75, 1.00, 1.15, 1.15, 1.15 22
[2]
[1]
10
20
30
40
Time / min
50
60
70
g reaction finished/copper sulfate gone, current
switched off (any of these)
[1]
4 a initial: 25, 26, 23, 24
final: 28, 39, 46, 58
rise: 3,13, 23, 34 [–1 for each incorrect value] [4]
b correct plotting [3] [–1 for each error], straight line [1]
(see graph below)
[4]
c extrapolation of line to 5 [1], correct reading of
temperature (44 °C) from extrapolation [1], units [1]
(see graph below)
[3]
50
40
Temperature rise / °C
1 Analysis of the substances we discover and use in
the wide variety of activities that shape our lives is
important in terms of our control of our environment,
the efficient use of resources available to us and our
protection from the harmful effects of contamination
and misuse. Chemical analysis can be used in
industry, medicine, agriculture and environmental
science. We need to know what chemicals we are
dealing with. Analytical techniques, from the simple
to the complex, help us to do just that. A medical
drug company might need to analyse the painkiller
paracetamol, for instance, in order to maintain the
purity of the product it is marketing. A steel-making
company must check if the content of a batch of steel
matched the customers requested composition. An
environmental analyst might have to check river water
for contamination with small amounts of metal ions,
which may be harmful to local wildlife and also in the
drinking water supply.
0
30
20
10
0
5
1
2
3
4
Number of carbon atoms in the alcohol formula
d temperatures would be higher [1], because copper is
a good conductor [1]
[2]
[1]
[1]
[1]
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
5 a chromatography [1]
b line below origin [1]
c inks colours would interfere with the result
(or words to that effect) [1]
d difference: A had more colours that B [1]; similarity:
both contained colour E [1]
[2]
e C,D and E [1]
23
Answers to end-of-chapter questions
6 a, b Provided in question as example answers.
c i
white precipitate that dissolves in excess
[3]
ii white precipitate, insoluble in excess d solid contained water (of crystallisation) e ammonia f E is not a sulfate [1], contains nitrate ions [1] [2]
[1]
[1]
[2]
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
Physics
mass
c density = volume [1]
102
= 25
1 a volume = l × b × h[1]
= 8.4 × 8.0 × 5.5
[1]
= 369.6 cm3[1]
[1]
= 4.08 g/cm3[1]
d
Sample m / g V2
V1
V / cm3 Density /
3
3
[1] / cm [1] / cm [1]
g/cm3 [1]
[1]
[1]
mass
b density = volume [1]
340
=
369.6 [1]
= 0.92 g/cm3[1]
2 mass of liquid = 203 – 147
[1]
[1]
= 56 g
density = mass
volume [1]
= 56
59 [1]
= 0.95 g/cm3[1]
3 a volume = l × b × h[1]
= 80 × 40 × 15
[1]
= 48 000 m3[1]
b mass = volume × density
[1]
= 48 000 × 1.3
[1]
= 62 400 kg
[1]
4 a Half-fill a measuring cylinder with water; record
volume.[1]
Place pebble in water, ensuring that it is submerged.[1]
Record new volume.
[1]
Volume of pebble equals difference in recorded
volumes.[1]
b mass of pebble
[1]
5 a 30.98 − 30.72
= 0.26 g
mass
b density = volume
[1]
[1]
0.26
= 200
[1]
= 0.0013
[1]
g/cm [1]
3
6 a V1 = 70 cm [1]
3
V2 = 95 cm3[1]
b V = 95 – 70
[1]
= 25 cm3[1]
24
7 a
b
c
d
e
B
144
80
44
36 [1]
4.0 [2]
C
166
124
71
53 [1]
3.1 [2]
water
volume (of water) or water level
the stone
volume (of water)
subtract or calculate the difference between
first volume from (or and) second volume
[1]
[1]
[1]
[1]
[1]
[1]
Chapter P2 Describing motion
distance
1 average speed = time [1]
= 400
50 [1]
= 8.0 m/s
[1]
2 distance = speed × time
[1]
= 15 × 30
[1]
= 450 m
[1]
3 a speed of light
b distance = speed × time
[1]
[1]
4 Speed is uniform (constant) in both.
[1]
The bus travels faster during B than A.
5 a
[1]
800
Distance / m
Chapter P1 Making measurements
Answers to end-of-chapter questions
600
400
200
0
0
10
20
30
Time / s
40
suitable scales chosen
[1]
horizontal axis and scale correct
[1]
vertical axis and scale correct
[1]
five points correctly plotted and straight line
drawn[1]
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
b Graph is straight line,
[1]
so constant speed.
[1]
6 speed is constant
[1]
acceleration = 0
[1]
Speed
7 a
Time
distance travelled
[1]
12 a average speed =
time taken
b m/s
[1]
cGraph is a horizontal straight line, showing that
speed does not change.
[1]
d distance travelled = area under graph
[1]
13 a 25 km
[1]
b i accelerating or increasing speed
ii steady or constant speed
iii decelerating or slowing down
c less than
[1]
[1]
[1]
[1]
14 a
[1]
[1]
[1]
30
Speed / m/s
horizontal axis showing time
vertical axis showing speed
rising straight-line graph starting at origin
Answers to end-of-chapter questions
b
20
10
Speed
0
horizontal straight-line graph above axis,
then decreases down to zero
[1]
[1]
8 a B, D
b A, E
c Acceleration is changing in the other section, C.
[2]
[2]
[2]
change in velocity
9 acceleration =
time taken
[1]
8.0
= 2.0 [1]
= 4 m/s2[1]
10 initial speed = 0 m/s
change in speed = acceleration × time
[1]
[1]
= 2.3 × 4.0
[1]
= 9.2 m/s
speed
11 time = acceleration [1]
[1]
24
= 5.6 [1]
= 4.3 s
25
[1]
10
20
30
Time / s
40
50
horizontal axis and scale correct
vertical axis and scale correct
six points correctly plotted
graph drawn through points
[1]
[1]
[1]
[1]
b acceleration = gradient of graph
[1]
Time
horizontal and vertical axes showing time and
speed[1]
0
27
= 30 [1]
= 0.9 m/s2[1]
c distance = area under speed against time graph [1]
= area of triangle + area of rectangle
[1]
1
= 2 × 30 × 27 + 20 × 27[1]
= 405 + 540
[1]
= 945 m
[1]
15 a iconstant/steady/uniform speed or velocity or
speed or velocity = 2.5 (m/s)
[1]
speed or velocity = 2.5 m/s
ii shape curving upward but not to vertical
[1]
[1]
bhorizontal (straight) line (parallel to time /
x-axis)[1]
c i horizontal straight line at 2.5 m/s from 0 to 2 s [1]
ii straight line rising to the right as far as the edge
of the graph area
[1]
Δv = 4 m/s or gradient clearly 2 m/s2[1]
dhorizontal straight line
[1]
at 0 m/s
[1]
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
Chapter P3 Forces and motion
1 resultant force
[1]
2 a weight
b friction
[1]
[1]
3 a weight downwards, air resistance upwards
[2]
b zero
[1]
c The resultant force on it is zero, so it does not
accelerate.[2]
4 a resultant force = 680 – 600
= 80 N
upwards
b He will accelerate upwards.
[1]
[1]
[1]
[1]
5 a weight = mass × g
[1]
= 80 × 10
= 800 N
b the same
c less
[1]
[1]
[1]
[1]
6 a force = mass × acceleration
[1]
b kilogram (kg) or gram (g); newton (N); metre per
second per second (m/s2)[3]
7 the bigger force acting on the smaller mass,
[1]
that is, the 10 N force acting on the 5 kg mass
[1]
8 force = mass × acceleration
[1]
= 20 × 5
[1]
= 100 N
[1]
force
[1]
9 acceleration = mass 1400 000
= 800 000 [1]
= 1.75 m/s2
[1]
change in speed
[1]
time
(20 – 12)
= 6.4 [1]
10 acceleration =
Answers to end-of-chapter questions
12 a the two 5000 N forces
[1]
They are equal in size but act in opposite
directions.
[1]
b resultant force = 1300 – 1200
= 100 N
[1]
[1]
forwards (to the left)
[1]
c The lorry will speed up (accelerate).
[1]
13 a i (engine) thrust and (air) friction
[1]
ii force shown vertically upwards, anywhere on
plane[1]
distance
b i speed = time in any form [1]
2200
= 2.75 [1]
= 800 (km/h)
[1]
ii idea of headwind on outward journey or tailwind
on return journey or routes of different lengths or
less friction or less weight
[1]
(v–u) or v or 8
14 a i
3 [1]
t
t
= 2.7 m/s2[1]
ii F = ma or 42 × 8/3
[1]
= 112 N
[1]
iii distance in first 3 s = 12 m
[1]
so distance in last 11.2 s = 88 m
[1]
88
so final speed = 11.2 = 7.9m/s[1]
b Any two from: lower top speed, longer total time,
less steep slope at first, etc.
[2]
Chapter P4 Turning effects of forces
1 moment
[1]
2 a resultant
b zero
[1]
[1]
3 a, b for example
[3]
= 1.25 m/s2[1]
force = mass × acceleration
[1]
= 1200 × 1.25
= 1500 N
[1]
[1]
11 weight = mass × g
[1]
= 50 × 1.6
= 80 N
[1]
[1]
26
centre
of
mass
centre
of
mass
stable object
unstable object
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
4 a
x
pivot
F
b moment = force × distance from pivot
c
Quantity
Unit
force
N
distance
m
moment of force
Nm
[1]
[1]
[3]
5 See Activity P4.03.
Make three small pinholes around the edge of the
lamina.[1]
Suspend the lamina freely from a pin through
one hole.
[1]
Mark a vertical line below the pin using a
plumb-line.[1]
Repeat this process for the other two pinholes.
[1]
The centre of mass is where the three lines
intersect.[1]
6
contact
force
A
1m
0.9 m
centre
of mass
B
1.5 m
weight
of beam
a centre of mass correctly marked, as in diagram
b arrows and labels added correctly
c moment of weight = force × distance
= 200 N × 0.5 m
= 100 N m
moment of force F is F × 1.0 = 100 N m
so F = 100 N
d upward contact force = sum of downward forces
= 200 N + 100 N
= 300 N
7 a force and perpendicular distance (of force)
from the point
b i
27
downward force arrow at centre of bar
[1]
[2]
[1]
[1]
[1]
[1]
[1]
[1]
[1]
[1]
[1]
[1]
Answers to end-of-chapter questions
ii 0.50 m or 50 cm
[1]
iii moment of force = 40 × 1.2 = 48 N m
[1]
moment of weight = + 30 × 0.5 = 15 N m
[1]
total clockwise moment = 48 + 15
= 63 N m
[1]
iv F × 0.2 = 63
[1]
63
F =
= 315 N[1]
0.2
v make bar longer or move pivot/stone to the left
or move pivot to left or increase mass of bar [1]
Chapter P5 Forces and matter
1 a increases
b decreases
[1]
[1]
2 If you stand upright, your weight is pressing down on a
small area.
[1]
This gives a high pressure.
[1]
If you use a ladder, the pressure is less because your
weight is spread over a greater area.
[1]
3 a extension = length when stretched – original
length[1]
b graph b[1]
4 a The extension of a spring is proportional to the
load, provided the limit of proportionality is not
exceeded.[2]
b load = stiffness × extension
[2]
c See Figure P5.05a.
[3]
5 extension = change in length
= 66 – 58
= 8.0 cm
[1]
[1]
[1]
6 extension for 5 N is 15 – 12 = 3.0 cm
[1]
extension for 15 N is 3 × 3 cm = 9.0 cm
[1]
length is 12 + 9 = 21 cm
[1]
7 See Activity P5.01.
Diagram or list indicating:
• spring hanging vertically from clamp
[1]
• weights hanging from end of spring
[1]
• ruler[1]
Student must measure:
• length of spring when weights added
• unstretched length of spring
• repeated for at least five different weights.
[1]
[1]
[1]
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
b
Load / N
Length / cm
Extension / cm
0.0
83.0
0.0
5.0
87.0
4.0 [1]
10.0
91.0
8.0 [1]
15.0
95.0
12.0 [1]
20.0
99.0
16.0 [1]
Extension / cm
2.0
60
40
20
0
0
20
1.0
0.5
0
5
10
Load / N
15
20
horizontal axis and scale correct
[1]
vertical axis and scale correct
[1]
five points correctly plotted and graph drawn
through points
[1]
force
9 a pressure =
[1]
area
F
b P = [1]
A
[3]
c
Quantity
Unit
28
80
1.5
0
10 a
b
Extension / mm
8 a
Answers to end-of-chapter questions
force
N
area
m2
pressure
Pa
40
Load / N
60
80
horizontal axis and scale correct
[1]
vertical axis and scale correct
[1]
eight points correctly plotted
[1]
graph drawn through points
[1]
c Draw up from 25 N to intersect graph line
[1]
from this intersection, go across to axis,
19 mm
[1]
d the point where the graph line ceases to be
straight[1]
40 N approximately
[1]
11 aextension indicated between two broken
lines[1]
b i four points correctly plotted
[2]
straight line through points and origin
[1]
ii proportional
[1]
iii 1 newton(s)
[1]
2 extension = 25 − 26 mm
length = 75 − 76 mm
Load / N
Length / cm
Extension / cm
0
3.200
0
10
3.207
7
b i two from
20
3.215
15
30
3.222
22
40
3.230
30
50
3.242
42
•
•
•
•
60
3.255
55
70
3.270
70
12 a wall A has bigger area
so lower pressure (on soil)
[1]
[1]
[1]
[1]
depth/height of air/atmosphere
density of air/atmosphere
acceleration due to gravity or weight of air
of air
[2]
ii 1 the same as
[1]
2 greater than or four times
[2]
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
Chapter P6 Energy transformations
and energy transfers
1
Answers to end-of-chapter questions
Name
Description
kinetic energy
energy of a moving object
useful energy output[2]
× 100 %
b efficiency =
energy input
1 2
8 a k.e. = 2 mv (m = mass, v = speed)[3]
bg.p.e. = mgh (m = mass, g = acceleration due
to gravity, h = height)
[4]
internal energy
energy stored in a hot object
9 work
chemical energy
energy stored in a fuel
potential / gravitational / p.e. / g.p.e. / position
[1]
light energy
energy that we can see
kinetic / k.e. / movement
[1]
sound energy
energy that we can hear
constant / the same / uniform [1]
strain (elastic)
energy
energy stored in a squashed
spring
joule(s) or J [1]
electrical energy
energy carried by an electric
current
nuclear energy
energy stored in the nucleus
of an atom
heat thermal
energy
energy escaping from a hot
object
2 a chemical energy → light + heat
10 a weight = mass × g[1]
= 180 × 1.6
[1]
= 288 N
[1]
b change in g.p.e. = weight × change in height
= 288 × 100
= 28 800 J
[1]
[1]
[1]
[9]
c g.p.e. increases
[1]
[2]
11 a mgh = 0.5 × 10 × 1.1
= 5.5 J
[1]
[1]
b electrical energy → kinetic energy
[2]
c kinetic energy → electrical energy
[2]
d kinetic energy → thermal (heat) energy
[2]
3 energy supplied = 100 J
energy released = 93 + 7 = 100 J
[1]
[1]
Energy before is equal to energy after, so energy is
conserved.[1]
4 a gravitational potential energy → kinetic energy
[2]
b kinetic energy → gravitational potential energy
[2]
cSome energy is lost as heat due to friction
and/or air resistance,
[1]
b i 1.5 (J)
c 9 + 5.5 = 14.5 J
[1]
1 2
k.e. = 2 mv [1]
v = 7.6 m/s
[1]
Chapter P7 Energy resources
[1]
5 a heat energy
[1]
2 a Trees and plants grow
b efficiency
[1]
c conservation
[1]
so the final g.p.e. cannot equal the original g.p.e. [1]
by jumping up as she starts off.
6 a thermal (heat) energy, electrical energy
[1]
[2]
b thermal (heat) energy
[1]
c Yes, because 90% of the energy is used,
[1]
and only 10% is wasted.
[1]
7 awaste energy = energy input – useful energy
output[2]
29
[1]
iienergy used to deform ball/ground or strain
energy stored in (deformed) ball/ground or
heat generated in deformed ball/ground
[1]
1 a
b
c
d
e
d She needs to supply energy,
[1]
resource
Sun
renewable
fossil fuels; non-renewable
wind, electricity
[1]
[1]
[1]
[2]
[2]
[1]
using sunlight as their energy source.
[1]
b Sunlight causes evaporation, producing
clouds;[1]
rain falls, and finally enters rivers,
[1]
whose water is trapped behind a dam.
[1]
3 a g.p.e.
b k.e.
c g.p.e. → k.e. → electrical energy
[1]
[1]
[2]
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
4 a i
Answers to end-of-chapter questions
fission
[1]
4 Ahmed
[1]
ii uranium
[1]
He lifts them to a greater height.
5 a Millie: speed = 25 = 0.50 m/s
50
100
= 0.40 m/s
Lily: speed =
250
b Millie
[1]
b i
fusion
[1]
ii hydrogen
[1]
iii helium
[1]
5 a Sunlight is always available in space, and not much
power is needed on a spacecraft.
[1]
But in cities, there are large numbers of people in a
small area,
[1]
so there is not enough roof space for all the solar
cells that would be needed to generate enough
power.[1]
b (for example) In a desert for roadside phones,
because there is then no need to connect
the phone to the mains electricity supply.
c A rechargeable battery can store the energy
produced by solar cells,
Because they are identical, the one with
the greater speed has the greater power.
[1]
7 a oil
nuclear fission
b i
gas lamp
[1]
ii electric motor or loudspeaker
[1]
iii microphone
[1]
Chapter P8 Work and power
1 a more
b more
[1]
[1]
2 a energy
b work
[1]
[1]
3 a work done = force × distance moved
(in the direction of the force)
[2]
b
[3]
Quality
Unit
W
joule, J
F
newton, N
x
30
metre, m
[1]
[1]
[1]
= 700 × 2.5
= 1750 J
[1]
[1]
gravitational potential energy (g.p.e.)
[1]
iiforce/mass/weight of (basket of) rocks
[1]
[1]
9
[1]
[1]
= 250 × 12.0
= 3000 J
b gain in g.p.e. = weight × increase in height
8 a i
[2]
[At least two correct in each column for 4 marks; deduct
1 mark for any in incorrect column.]
[1]
7 a work done = force × distance moved
6 Renewable: two from hydroelectricity, solar, tidal,
wind[2]
Non-renewable: two from coal, oil, nuclear
[1]
[1]
[1]
and can therefore supply electricity when the sun is
not shining.
[1]
[1]
6 work done = energy transferred
[1]
[1]
[1]
and height of cliff
b chemical energy
[1]
c time taken
to raise basket up cliff
[1]
[1]
a weight = mass × g[1]
= 45 × 10
= 450 N
[1]
b gain in g.p.e. = weight × increase in height
= 450 × 0.20 × 36
[1]
[1]
= 3240 J
[1]
work done
[1]
c power =
time taken
3240
= 4.2 [1]
= 770 W
[1]
= 0.77 kW
[1]
10 a work done = force × distance moved
[1]
= 780 × 100
[1]
= 78 000 J
[1]
b work done = force × distance moved
[1]
= 240 × 100
[1]
= 24 000 J
[1]
[9]
1
2
c k.e = × 750 × 12 [1]
= 54 000 J
2
[1]
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
dwork done by engine = work done against
friction + k.e.
[1]
so energy is conserved
[1]
11 a M = V × D = 103 × 10-3[1]
= 1.0 kg
[1]
b mgh = 1 × 10 × 0.8
[1]
= 8.0 J (or 8.0 N m)
E 8 × 90
c P= =
t
60
= 12 W (or 12 J/s or 12 N m/s)
[1]
so the average energy of the molecules
remaining decreases.
[1]
[1]
Hence its temperature decreases.
[1]
1 See Figure P9.01 in the Coursebook.
[6]
2 See Figure P9.03 in the Coursebook.
[3]
3 a evaporation
b faster-moving or more energetic; decrease
or fall/drop
[1]
[2]
4 a gas
b solid
c liquid
[1]
[1]
[1]
5 a solid
b The particles are well separated and can move
about within the volume of their container,
[1]
colliding with its walls and with each other.
[1]
[1]
[1]
b temperature
[1]
7 a smoke particles
b molecules of the air
[1]
[1]
8 a particles of smoke
[1]
b The smoke particles are moving because the
particles of the air are continually colliding with
them,[1]
[1]
9 a slowly
[1]
b quickly
[1]
c quickly
[1]
bIn the liquid, forces between the particles hold
them together.
31
[1]
[1]
Chapter P9 The kinetic model of matter
10 a evaporation (or vaporisation)
so that its mass decreases.
[1]
8000 Pa (or 8000 N/m2)[1]
changing their speed and direction of motion.
11 aMolecules of ethanol leave the surface of the
liquid[1]
bThe more energetic molecules of ethanol
are more likely to leave the liquid,
d P = ρgh[1]
6 a energy
If it is to become a gas, energy must be supplied
to overcome these forces and separate the
particles.[1]
[1]
78 000 = 24 000 + 54 000
Answers to end-of-chapter questions
[1]
[1]
12
Shape
Molecules
a
Solid
fixed shape [1]
vibrate about a
fixed position
b
Liquid
shape fills the
container from
the bottom [1]
move around,
close together
c
Gas
completely fills
the container
move around,
far apart
[1]
[1]
13 a ibombardment/collisions with air molecules/
particles[1]
ii any two from
lighter / very small / smaller than smoke
particles / too small to be seen fast-moving /
high kinetic energy random movement /
movement in all directions
[2]
b i increases
[1]
iiair molecules/particles/atoms bombard/
hit walls
[1]
molecules faster / higher energy when
temperature raised
[1]
(not vibrate faster) greater force (per unit area)
or more collisions per second
[1]
Chapter P10 Thermal properties of matter
1 a See examples in Section P10.01 of the Coursebook. [1]
b See examples in Section P10.01 of the Coursebook. [1]
2 a Liquid in bulb absorbs energy; gets hotter; expands;
pushes up tube.
[3]
b melting point of pure ice (0 °C); boiling point of pure
water (100 °C)
[2]
3 a Mercury expands as its temperature increases.
[1]
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
b
Definition
Value
lower
fixed point
melting point
of pure ice
0 °C
upper
fixed point
boiling point of
pure water [1]
100 °C
b Electrons collide with particles in hotter region, gain
energy; move randomly to cooler region, collide with
particles there, give them energy. [3]
[1]
c (for example) the resistance of a resistor
or thermistor
4 expands; greater; less; lighter; rises; more; gravity;
convection[8]
5
[1]
4 a A has greater range (120 °C, from –10 °C to +110 °C).
(B’s range is only 60 °C, from –10 °C to +50 °C.)
[2]
b B is more sensitive. Each degree is a wider interval on
the scale, so smaller changes can be measured. [2]
5 solids, liquids, gases[3]
6 a the thermocouple thermometer
b 100 °C
[1]
[1]
This is a fixed point on the Celsius scale.
c the liquid-in-glass thermometer
[1]
[1]
It can measure to 0.5 °C (or better);
the other measures to the nearest 1 °C.
[1]
d The properties of the two materials used in
the thermometers do not vary linearly with
temperature.[1]
The voltage of the thermocouple does not
increase at a steady rate as the temperature
goes up.
7 a 0 and 100 (°C)
b i
[1]
[1]
expands
[1]
ii moves along the tube/up/to the right
[1]
stops at/near 100 mark
[1]
c arrow slightly to left of –10 mark
b metal; non-metal
2
convection
Warm fluid moves, carrying
energy with it.
radiation
Energy travels as infrared waves.
conduction
Energy travels through a material
without the material moving.
Good emitter
Good reflector
matt
[1]
matt
[1]
shiny
[1]
black
[1]
black
[1]
white
[1]
6 a As the air is heated, it expands.
[1]
Its density decreases.
[1]
It is lighter than the surrounding air, so it floats
upwards.[1]
b The surrounding air is cooler and so less dense.
[1]
It sinks and replaces the warm air rising above the
flame.[1]
7 a Particles at the hot end have greater energy, so
vibrate more.
[1]
They collide with neighbours, sharing energy with
them.[1]
Energy is thus transferred from the hot end to the
cold end.
[1]
b The temperature of the cold end of the rod would
rise more rapidly,
[1]
because metals are better conductors than
plastics.[1]
c electrons
[1]
8 a walls made of glass – poor conductor
[2]
[1]
[3]
lid – prevents convection losses
(but see part b)[2]
[2]
silvering – reflects away infrared radiation
[2]
bA liquid that is colder than its surroundings does not
heat the air above it,
[1]
so no convection current rises above it. Hence a lid is
not essential.
[1]
9 aAir is a good insulator, so less heat is lost by
conduction.[1]
[2]
3 a Particles in hotter region vibrate more; collide
with cooler neighbours and share energy; these
vibrate more, pass energy on to their neighbours;
and so on.
[3]
32
Good absorber
vacuum between walls – no conduction or
convection[2]
Chapter P11 Thermal (heat) energy transfers
1 a temperature; higher; lower
Answers to end-of-chapter questions
Cold air from the window cannot flow into the
room, so convection current losses are reduced. [1]
bInfrared (heat) radiation from below is reflected
back into the house,
so that less escapes from the house.
[1]
[1]
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
cThe glass wool prevents the movement of air in the
gap, so it is difficult for a convection current to be
set up,
[1]
c The vibrations of the instrument cause the air near
the instrument to vibrate.
[1]
which would transfer energy from the inner wall to
the outer wall.
[1]
10 a i conduction
[1]
ii convection
[1]
b heat lost at same rate as heat supplied
[1]
c i boiling
[1]
ii steam
[1]
11 a i conduction
[1]
[1]
[1]
[1]
[1]
The frequency of trace C is the greatest (because more
waves are contained in the same time interval).
[1]
7 You need a source of sound,
and two detectors in line with the sound.
[1]
[1]
You need to measure the distance between the two
detectors,[1]
and the time interval between the sound reaching
them.[1]
distance
Then use speed =
time
to calculate the speed of sound.
[1]
8
Chapter P12 Sound
1 a source
and these propagate through the air to the
listener’s ear.
b trace C
[1]
[1]
[1]
[1]
[1]
[1]
The amplitude of trace A is the greatest.
bcopper is a better conductor or iron is a worse
conductor[1]
c iron conducts heat slowly
so gas above gauze is hot enough to burn
copper conducts heat rapidly
so gas above gauze is not hot enough to burn
Compressions and rarefactions are formed,
6 a trace A
iiatoms/free electrons at hot end vibrate more/
have more energy
[1]
share energy with others by collisions
Answers to end-of-chapter questions
rarefaction
where particles of the medium are
spread out
compression
where particles of the medium are
squashed together
[1]
[1]
b vibrations
[1]
c echo
[1]
d frequency; second
[2]
tap table at a distance
[1]
e hertz
[1]
and hear the sound through the wood.
[1]
f
[2]
c distance travelled = 2 times length of rod
2 a greater frequency
[2]
b greater amplitude
[2]
gases; vacuum
3 a
B A
[2]
b
D
[2]
C
9
a solid
[1]
b (for example) Place ear against table,
= 800 m
[1]
distance
[1]
time
800 m
= 0.16 s [1]
= 5000 m/s
[1]
speed =
10 a i reflection or wave bounces back
[1]
from large object/sea bed
[1]
ii distance = speed × time
[1]
= 1500 × 0.80
[1]
= 1200 (m)
[1]
iii 1200/2 = 600 (m)
[1]
b graph should show
4 shaded from 20 Hz to 20 kHz
[2]
5 a the air inside the instrument
[1]
uniformly sloping line
[1]
b the strings of the instrument
[1]
with positive gradient
[1]
33
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
11 a any large surface, e.g. wall / cliff / mountain
b i when hears bang / sees flash
[1]
Two rays in different directions
from a single point on the lamp
[1]
reflect off the mirror correctly
[1]
and are extrapolated back behind the mirror,
[1]
so that the image is at the point where they cross. [1]
[1]
ii when hears echo
[1]
c i reading = 2.25 s
[1]
distance
[1]
time
720
=
[1]
2.25
= 320 (m/s)
[1]
speed =
Answers to end-of-chapter questions
ii one from
b Each ray is reflected
[1]
so that angle of incidence equals angle of
reflection.[1]
6 a
ray 2
inaccurate distance from firework
I
F
ray 1
F
reaction time
wind
[1]
Ray 1 continues straight through the centre of the
lens,[1]
ray 2 bends at the lens
[1]
and passes through the principal focus F,
[1]
so that the image is at the point where they cross. [1]
Chapter P13 Light
1 a See Figure P13.01 in the Coursebook.
[4]
b angle of incidence = angle of reflection
i = r[2]
2 a virtual
b The image is diminished
[1]
because it is shorter than the object.
b the same size as
[1]
c object
[1]
d left–right inverted
[1]
7 See Figure P13.03a in the Coursebook.
[2]
8
3 See Figure P13.08a in the Coursebook.
4
O
incident ray
[1]
c The image is inverted because it is below the axis. [1]
normal
mirror
angle of
incidence i
[1]
[5]
aRay diagram correctly drawn showing that the ray
passes through both surfaces undeflected, that is,
the ray remains straight.
[2]
b
angle of
reflection r
reflected ray
incident and reflected rays
correctly drawn
[1]
normal correctly drawn
[1]
angle of incidence correctly marked
[1]
angle of reflection correctly marked
[1]
5 a
9
image
mirror
object
34
ray bends towards normal
then away again
so that it ends up parallel to original path
[1]
[1]
[1]
c Parallel rays remain parallel.
[1]
a converging
[1]
b closer than
[1]
c virtual; magnified
[2]
10 a n =
speed of light in a vacuum
[2]
speed of light in the material
b
n = refractive index, i = angle of incidence,
r = angle of refraction
[3]
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
11 See Figure P13.05a in the Coursebook.
12 a
30° 30°
A
[6]
50° 50°
Answers to end-of-chapter questions
Chapter P14 Properties of waves
1 energy; matter
[2]
2 a bounces off
[1]
b speed
[1]
B
3 reflection, refraction (in either order)[2]
4 a 4.0 cm
[1]
b 3.0 cm
[1]
c one wave = 4 cm so 10 cm = 2.5 waves
[1]
In block A, reflected ray at equal angle
[1]
and refracted ray bent away from normal.
[1]
so 2.5 waves pass in 1 s
[1]
In block B, reflected ray only,
[1]
frequency = 2.5 Hz
[1]
at equal angle.
[1]
1
[1]
there is only an internally reflected ray;
[1]
all of the ray is totally internally reflected.
[1]
1
2
3
4
5
6
7
8
9
x / cm
–2
parallel to axis to lens and on through focal point
undeviated through centre of lens
traced back to locate image
0
–1
13 a i any two of these three rays from top of object:
as if from focal point to lens and then parallel
to axis
[2]
2
y / cm
bWhen the angle of incidence is greater than the
critical angle,
d
correct value of amplitude
[1]
correct value of wavelength
[1]
waves correctly reflected at barrier
[1]
separation remains as before
[1]
5
[1]
ii any two of:
virtual / upright / magnified / further from
lens / dimmer
b i 3.4–3.6 cm
[2]
[1]
ii magnifying glass[1]
14 a i image behind mirror
image same distance from mirror, along line
perpendicular to mirror
[1]
[1]
ii reflected ray reaching eye
[1]
direction of reflected ray coming from
image[1]
b HIS, because S is not its own mirror image
[1]
c both rays straight on at first surface
[1]
30° prism ray refracted down in air at second
surface[1]
45° prism ray reflected down in glass at second
surface[1]
90° reflection
[1]
straight on at third surface
[1]
35
6
7
transverse
describes a wave that varies from
side to side, at right angles to the
direction of travel
longitudinal
describes a wave that varies back
and forth along the direction of
travel
Symbol
Quantity
v
speed
f
frequency
λ
[1]
Unit
m/s
[1]
[1]
Hz
[1]
wavelength [1]
m
[1]
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
8 a decreases
b stays the same
c decreases
[1]
[1]
[1]
Answers to end-of-chapter questions
b radio waves = lowest frequency, longest wavelength
gamma rays = highest frequency, shortest
wavelength[2]
9 a speed = frequency × wavelength, v = f λ[1]
b v = f λ = 6 × 1014 × 3.75 × 10−7[1]
= 2.25 × 108 m/s
[1]
3 a false
[1]
b true
[1]
10
4 300 000 000 m/s = 3.0 × 10 m/s
[1]
5 a electromagnetic
[1]
short
[1]
c true
[1]
8
b film or photographic film or electronic detector
or charge-coupled device (CCD)
[1]
c absorbed/stopped by bone (not deflected/
reflected)[1]
less absorption by flesh or penetrates/passes
through flesh
waves are curved in space beyond barrier
[1]
separation remains as before
[1]
11 a i
amplitude[1]
ii wavelength
b i string moves air
[1]
[1]
backwards and forwards or up and down or
produces compressions and rarefactions
[1]
ii gets quieter/softer/less loud
[1]
12 a i R in correct position, by eye
[1]
iithree reflected waves correctly meeting
mirror[1]
three reflected waves equidistant and
centred on R
b first ray plus reflection correct
second ray plus reflection correct
reflected rays projected back, to meet behind
mirror or labelled I and in correct position
[1]
[1]
[1]
[1]
[2]
b red = lowest frequency, longest wavelength
violet = highest frequency, shortest wavelength
[2]
2 a radio waves, microwaves, infrared, visible light,
ultraviolet, X-rays, gamma rays
[2]
36
d any one of:
photographic film badges, behind screen when
operating X-ray machine, protective clothing,
minimise exposure
[1]
Chapter P16 Magnetism
1 a i
repel
[1]
ii attract
[1]
b See Figure P16.02 in the Coursebook.
2 a i
[2]
soft
[1]
ii hard
[1]
b i
for example: steel
[1]
ii for example: soft iron
[1]
3 a See Figure P16.04a in the Coursebook.
[1]
b See Figure P16.04b in the Coursebook.
[1]
4 a one of the following:
electromagnet can be switched on and off
strength can be varied by changing current
Chapter P15 Spectra
1 a red, orange, yellow, green, blue, indigo, violet
[1]
poles can be reversed by reversing current
[1]
b one of the following:
N and S poles at opposite ends
field lines have same pattern
[1]
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
5 a
2
repel
1
N
Answers to end-of-chapter questions
a left-hand end of solenoid N
[1]
right-hand end of solenoid S
[1]
attract
S
b lines of force out of N poles and into S poles
3
N
N
[1]
lines close together at poles, farther apart
elsewhere[1]
S
attract
S
N
S
repel
each correct pair of attractive or repulsive forces [4]
N
repulsion indicated by distortion of pattern
[1]
b i
S
S
N
N
S
S
with attractive forces shown
[1]
6 a bigger current
[1]
more turns of wire or turns of wire closer together [1]
add an iron core
[1]
b (for example) in a scrapyard crane or an
electromagnetic door bolt
[1]
7 a A soft magnetic material is easy to magnetise
[1]
and to demagnetise.
[1]
A hard magnetic material is difficult to magnetise
and demagnetise.
[1]
b A hard material
[1]
because it retains its magnetisation well.
c A soft material
[1]
[1]
because its magnetisation can change easily.
8
[1]
[1]
Switch closed
Switch open
Soft iron
magnetised
loses its
magnetism
Steel
magnetised
keeps its
magnetism
attractive force
[1]
iii
with soft iron core
[1]
iv
can be switched on and off (or can be
stronger)[1]
10 a can be switched off
[1]
can vary the strength
[1]
b i 1000 turns
ii iron
iii 3.0 A
[2]
Chapter P17 Electric charge
1 a rubbed, friction, opposite
[3]
b repel, attract
[2]
2 a electrons
[1]
b negative
[1]
c positively
[1]
3
Quantity
Unit
Symbol for unit
force
newton
N
electric charge
coulomb
C
4 a positive
S
N
N
S
[2]
ii
N
magnets in a square arranged
N–S–N–S–N–S–N–S[1]
37
[1]
9 a (S) N S N
4
b
similar pattern for both magnet and solenoid
[4]
[1]
b They are equal.
[1]
c Suspend one so that it can turn freely.
[1]
Bring the other close to one end and observe
repulsion.[1]
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
5 a i
iron or ferromagnetic
unmagnetised (before being brought near
magnet)[1]
(not non-magnetic)
[1]
Answers to end-of-chapter questions
5
cell
ii magnet
[1]
b attracts (at first)
[1]
repels after touching or angle of thread increases
as XY decreases
[1]
6 a rub/rubbing
[1]
with dry cloth
[1]
b i
current
switch
negative (−)
[1]
ii opposite charges attract
[1]
c horizontal arrow to L, starting or ending
on sphere
[1]
d swings to R / moves away / is repelled
[1]
lamp
a series circuit correctly drawn
[1]
correct symbols with labels
[3]
b at least two arrows around circuit
[1]
from positive of cell
[1]
c voltmeter
[1]
d volt (V)
[1]
+
6
–
Chapter P18 Electrical quantities
1 a charge
[1]
b positive, negative
[2]
2 a ammeter, series
[1]
b voltmeter, parallel
A
[1]
3 a
R
A
V
a correct symbols for resistor, ammeter and power
supply[3]
[4]
V
V
b R = [1]
I
4
38
Unit
Potential difference
volt [1]
Current
ampere
Resistance
ohm [1]
Symbol for unit
[1]
V
[1]
A
[1]
Ω
[1]
connected in series
[1]
with voltmeter in parallel with resistor
[1]
b current
[1]
c potential difference (p.d.)
[1]
V
d R = [1]
I
6.5
[1]
=
1.25
= 5.2 Ω
[1]
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
7
Equation
In words
In units
Q = It
charge = current × time [1]
coulomb = ampere × second
(C = A s)
R=
8
Answers to end-of-chapter questions
V
I
resistance =
p.d.
[1]
current
P = IV
power = current × p.d. [1]
E = IVt
energy = current × p.d. × time
[1]
ohm = volt/ampere
(Ω = V/A)
[1]
watt = ampere × volt
(W = A V)
[1]
joule = ampere × volt × second
(J = A V s)
Q
a I= [1]
t
30
= [1]
20
= 1.5 A
[1]
9
= 1.5 × 10 × 20
[1]
= 300 J
[1]
a i
[1]
10 a light
[1]
b heat
[1]
c power = 36 W
[1]
d energy = power × time
[1]
= 36 × 60
[1]
b E = Pt[1]
= IVt[1]
[1]
= 2160 J
[1]
P
e I = [1]
V
30
[1]
= 12
= 3 A
[1]
A
Chapter P19 Electric circuits
coil of
wire
1 a current
[1]
b sum
[1]
each symbol correctly drawn
[4]
2
V
battery/cell, ammeter, coil in series
[1]
voltmeter in parallel with coil
[1]
standard symbols used for battery/cell,
voltmeter and ammeter
[1]
V
ii R = [1]
I
iii any two of:
length (of wire) diameter/cross-section/
area (of wire) resistivity/type of material
temperature[2]
6.0
b R = [1]
1.5
= 4.0 Ω
[1]
39
resistance of AB = 1.0 Ω
[1]
resistance per metre = 0.50 Ω/m
[1]
3 a melting, burning, fumes
[1]
b wire melts, breaks circuit
[1]
c Fuse will not break for normal current, but will break
when current rises above this value.
[1]
4 a voltage (or p.d.)
[1]
b shared
[1]
c more (greater)
[1]
5 a series
[1]
b parallel
[1]
c series
[1]
d parallel
[1]
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
6
Name of device
9
Description
light-dependent
resistor (LDR) [1]
resistance
decreases
[1]
when light
falls on it
thermistor [1]
resistance
[1] changes when
temperature
changes
7 a
8
Circuit symbol
6V
series circuit
[1]
correct symbols for resistor, switch and
power supply
[3]
b 10 + 40
[1]
= 50 Ω
[1]
c 0.12 A
[1]
d 0.12 A
[1]
a wires overheat (risk of fire)
[1]
b fuse, trip switch
[2]
c Use thicker wires,
[1]
which have lower resistance,
[1]
so there is less heating.
[1]
a in parallel
[1]
b 6.0 V
[1]
across each resistor
c The 2 Ω resistor,
because the resistance is lower.
[1]
Answers to end-of-chapter questions
1 1 1
ii = + [1]
R 3 6
R = 2 Ω
[1]
V
[1]
c I= R
= 6.0 A
[1]
d i stays the same
[1]
ii decreases
[1]
Chapter P20 Electromagnetic forces
1 current, magnetic, circles (or circular), wire
[4]
2 current, magnetic, turning, rotate
[4]
3 a The wire will swing the other way.
[1]
b The wire will swing the other way.
[1]
4 a force (motion)
[1]
b magnetic field
[1]
c current
[1]
5 a downwards
[1]
b to the right,
[1]
by Fleming’s left-hand rule
[1]
6 a downwards
[1]
b upwards
[1]
c The forces are unbalanced,
[1]
and so provide a turning effect.
d The force is zero,
[1]
because the current does not cut across the
magnetic field (it is parallel to the field).
7 a i
[1]
[1]
current clockwise when viewed from top
[1]
ii anticlockwise or down on left and/or up
on right
[1]
b i
[1]
faster or greater turning effect
[1]
ii faster or greater turning effect
[1]
[1]
iii faster or greater turning effect
[1]
1 1 1
d = + [1]
R 2 3
3 2 5
+ = [1]
6 6 6
6
[1]
R = = 1.2 Ω 5
V 6
R = = [1]
R 1.2
= 5.0 A[1]
Chapter P21 Electromagnetic induction
1 conductor, magnetic, induced, circuit, current
[5]
2 (answers from the top) d.c.; a.c.; a.c.; d.c.; a.c.; d.c.; a.c.
[7]
3 coil, rotate/turn, magnetic, e.m.f., current
[5]
4 high, smaller, less
[3]
5 a primary, core, secondary
[3]
10 a i 4.0 V
[1]
b step-up, e.m.f./voltage
[2]
ii 12 V
[1]
c step-down, e.m.f./voltage
[2]
b i 6 Ω
[1]
40
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
Answers to end-of-chapter questions
6 Vp = p.d. across primary coil
d stronger magnetic field
[1]
turn the coil faster
[1]
Vs = p.d. across secondary coil
Np = number of turns on primary coil
Ns = number of turns on secondary coil
[4]
11 a
7 Ip = current in primary coil
Vp = p.d. across primary coil
Vp Np
= [1]
Vs Ns
5000 × 12
[1]
Ns =
230
= 261
[1]
b Ip × Vp = Is × Vs[1]
Is = current in secondary coil
Vs = p.d. across secondary coil
[4]
8 aThe magnetic field around the wire is
changing (it is cutting across field lines).
0.40 × 12
[1]
230
= 0.021 A
[1]
Ip =
[1]
bIt will change sign / direction (from positive to
negative, or the other way round).
[1]
c She should move the wire more quickly.
[1]
d No,
[1]
Chapter P22 Atomic physics
1
electron
nucleus
proton
because it is not cutting across the field lines /
the magnetic field is not changing.
[1]
9 a so that less energy is lost during transmission
[1]
Vp Np
= [1]
Vs Ns
Vs = Vp × Ns[1]
Ns
3 × 200
= 60 V
[1]
10
cUse the primary coil as the secondary and the
secondary as the primary.
[1]
b
10 a i X: coil
[1]
ii Y: slip rings
[1]
iii Z: brushes
[1]
b A.c. flows back and forth, changing direction.
D.c. flows in one direction only.
[1]
d.c.
Current
neutron
4
2 He
2
Name
What it tells us
X
chemical symbol [1]
name of element [1]
Z
proton number [1]
number of protons in
nucleus [1]
A
nucleon number [1]
number of nucleons in
nucleus [1]
3 proton number + neutron number = nucleon number [1]
4 a different numbers
[1]
b the same number
[1]
c different numbers
[1]
5 a 6 protons
[1]
Time
b 6 neutrons
[1]
a.c.
c 6 electrons
[1]
6 a 79 + 118
–
= 197
197
79
[1]
[1]
[1]
b
c more turns
[1]
7 a 19
[1]
bigger area
[1]
b 39
[1]
correct (labelled) diagram
c
41
Symbol
[1]
+
0
[4]
40
19
Au[2]
K[2]
© Cambridge University Press 2017
Cambridge IGCSE Combined and Co-ordinated Sciences
8
Radiation
alpha
Penetration least
penetrating
gamma
in between
most
penetrating [1]
Absorption
most easily in between
least easily
absorbed
[1] absorbed [1]
Absorbed
by
thin paper,
a few cm
of air
7
9
beta
thin metal
thick lead or
foil [1] concrete [1]
a (average) time, half, decay
[3]
b See Figure P22.08 in the Coursebook.[3]
10 β is more penetrating than α.
[1]
Detect using Geiger counter.
[1]
Place thin paper over sources − α does not pass
through.[1]
Place thin aluminium foil over sources − neither
passes through.
[1]
11 a it has negative charge
[1]
12
42
b charged; Fleming’s left-hand rule
[2]
c it is uncharged
[1]
Use
… because …
Finding the age of
an object
radioactive substances
decay at a known rate.
Seeing through
solid objects
radiation can penetrate
matter.
Sterilising
medical
equipment
radiation can destroy living
cells.
Tracing the
movement
of hazardous
substances
small amounts of radiation
can be detected.
Answers to end-of-chapter questions
13 a i 3
[1]
ii 3
[1]
iii 4
[1]
iv 3 + 4 = 7
[1]
b
14 a
Li
[1]
7
3
Particle
Charge
Mass
electron
−1
m
neutron
0
[1]
2000m
[1]
proton
+1
[1]
2000m
[1]
b i 92
[1]
ii 146
[1]
iii 92
[1]
15 a i proton
[1]
ii proton and neutron
[1]
b number of protons = 47
[1]
number of neutrons = 107 − 47 = 60
c i 8 h ± 0.25 h
[1]
[1]
iiChoose two points on the graph; for each,
halve the value and add 8 h to the time.
[2]
[4]
© Cambridge University Press 2017